Management of Hard Rock Basaltic Aquifer through Aquifer Mapping: A Case Study of Nashik District, Maharashtra, India

Abstract

In the Maharashtra State of India, Deccan Trap basaltic lava flows are spread over around 82% of the area and form the most prominent aquifer in the entire state. Nasik district occurring in the northern part of Maharashtra also known as Khandesh represents a typical area of Deccan Trap basalt. The storage and transmission capabilities of the basaltic lava flow aquifer are very limited due to the inherent absence of primary pore spaces. These basaltic rocks act as aquifers only when they are weathered, jointed or fractured, thus giving rise to secondary porosity and permeability. Due to wide variations in secondary openings, the potential areas for groundwater are generally localized. In this way, Deccan Trap basalt possesses a unique challenge to aquifer mapping, both spatially and vertically due to its hydrogeological heterogeneity. In the current study, this challenge of aquifer mapping and management in basalt was tackled through a multidisciplinary, multipronged approach involving data integration of various thematic layers viz., geomorphology, soil, drainage, land use-land cover, hydrometeorology, and geophysical techniques etc., as indirect tools and combining it with direct tools such as drilling, well inventory, water level monitoring, groundwater quality checks, and aquifer pumping tests for obtaining reliable results. By following the above methodology, the 3-D aquifer geometry, lithological sections, fence diagrams, aquifer characteristics, yield potentials, and aquifer-wise resources were deciphered. The results showed that the area has two aquifer systems comprising of Aquifer-I, that is. shallow aquifer, which is generally tapped by the dug wells of 8 to 32 m depth with water levels of 1.2 to 15 meters below ground level (m bgl) and yield varies from 10 to 100 m3/day. Whereas, the Aquifer-II, that is, deeper aquifer is being tapped by bore wells with a depth ranging from 30 to 200 m bgl and a water level from 8 to 55 m bgl. However, their pumping sustainability was limited to 0.5 to 3 hours due to low storage potential resulting in overexploitation. The given aquifer maps indicate that major parts of the area have limited yield (Aquifer-I: between the depth of 10 m - 15 m bgl and Aquifer-II: between the depth of 80 m −140 m bgl). In hard rock areas, especially basaltic aquifers due to their low storage potential, groundwater development is always a challenging task unless it is combined with the management of the resources. Considering the issues plaguing the area, the aquifer management plan encompassing supply and demand-side interventions, and groundwater development has been devised. It is concluded that 139.30 MCM of groundwater resources can be augmented by artificial recharge under supply-side interventions. Whereas the groundwater demand for irrigation can also be reduced by 272 MCM by adopting drip irrigation in 117 sq. km. of sugarcane and 790 sq. km. of onion cultivated areas under the demand-side interventions. The implementation of these measures will minimize the stress on groundwater by bringing down the stage of groundwater development from 88–55% (safe category) in six water-stressed blocks/taluka, whereas the overall stage of groundwater development will be reduced from 58.45% to 40.70%. Thus, the adoption of both supply-side and demand-side interventions interlinked with water budgeting through community participation will provide long-term solutions to combat the overexploitation, water level decline, low storage potential, recurring droughts and other issues of the area and also help in improving socioeconomic conditions of the area.

1. Introduction

Groundwater is often referred to as an invisible resource, controlled by many natural factors such as physio-climatic conditions, geomorphology, topography, soils and the most important being the geology thereby hampering its sustainable development and management. However, when groundwater is hosted by a hard rock aquifer, its quantifiable attributes become even more unpredictable, and site-specific, thus making it a challenge to devise a suitable management plan. Aquifer mapping is one such tool to effectively manage hard rock aquifers. Aquifer mapping is a process wherein a combination of geological, geophysical, hydrological, and chemical analyses is applied to characterize the quantity, quality, and sustainability of groundwater in aquifers.

The activities include the collection and interpretation of data available from groundwater from various authentic sources. Having plotted the data on maps the data gaps are identified by micro-level data acquisition, that is. through the drilling of bore wells down to the depths of 200 meters and the generation of records of requisite data. Hydrological and hydrometeorological studies for recharge estimation and extensive quality monitoring to assess the potability of groundwater for various uses. Conducting various aquifer performance tests to ensure the yield potential of the aquifer and its sustainability for optimum pumping is the next step followed. Using all these data and data sets various maps have been prepared to draw the 3D geometry of the shallow and deeper aquifers occupying up to 200 m bgl in the area. Both quality and quantity have been assessed to ascertain groundwater availability and safe development (exploitation) in the study area. GIS technology has been used widely for the preparation of various aquifer maps and also to draw the aquifer management plan forming a part of National aquifer mapping (NAQUIM) [1].

In the Maharashtra state of India, Deccan Trap basaltic lava flows are spread over around 82% of the area and form the most prominent aquifer in the entire state. The storage and transmission capabilities of the basaltic lava flow aquifer are very limited due to the inherent absence of primary pore spaces. These basaltic rocks act as aquifers only when they are weathered, jointed, or fractured thus giving rise to secondary porosity and permeability. Due to wide variations in secondary openings, the potential areas for groundwater are generally localized. Thus, Deccan Trap basalt possesses a unique challenge to mapping the aquifer both spatially and vertically due to its hydrogeological inhomogeneity.

2. Materials and methodology

The aquifer mapping study under NAQUIM was taken up by Central Ground Water Board (CGWB) in 3 phases and completed in March 2022. One of the important aspects of aquifer mapping is data gap analysis because it determines the optimum data, which is required to be generated after considering the existing available data as per the aquifer mapping protocols. Without the availability of sufficient data, a true picture of the area cannot be generated [2]. The available data of the exploratory wells, groundwater level monitoring stations, micro-level hydrogeological data acquisition, and groundwater quality monitoring stations of CGWB were compiled and analyzed for adequacy. In addition to these, the data on groundwater monitoring stations and groundwater quality stations of the groundwater survey and development agency (GSDA) was also utilized [3]. After taking into consideration the available data on groundwater exploration, geophysical survey, monitoring, and quality, the data adequacy has been worked out considering the heterogeneity of aquifers in the area.

The thematic layers of geomorphology, soil, drainage, and land use-land cover were not available, hence considered as a data gap. The data gap analysis was done for major parameters namely, exploratory drilling data, micro-level hydrogeological data (acquisition from the key well inventory/establishment), groundwater monitoring data, and groundwater quality data. The data gap is arrived at by considering the requirement and the existence in the grid pattern whose details are as follows -

• Exploratory wells = 14 wells (details available, but not adequate as per the grid-pattern requirement)

• Gaps = 50 wells (instead of 40 wells)

• Micro-level data gap = 148 wells

• Water level monitoring wells = 154 wells (quality data gaps)

Considering the data gaps, feasibility and availability of locations, additional data on exploratory wells, micro-level hydrogeological well inventory, water level monitoring, and groundwater quality was generated (Table 1). The drilling data of 61 wells comprising exploratory wells, observation wells, and piezometer was used to prepare the subsurface lithology, hydrogeological cross sections, fence diagram, and aquifer maps. The water level data of 215 monitoring wells of CGWB and GSDA of Aquifer-I, and 55 wells of Aquifer-II of CGWB was utilized to depict the aquifer-wise water level scenarios during pre-monsoon and post-monsoon seasons. The long-term water level data for the period 2012–2021 was available for 185 monitoring wells out of 215 wells, and it was analyzed to depict the water level trends for Aquifer-I. The groundwater samples collected primarily during the pre-monsoon season from 128 dug wells, and 35 borewells were analyzed for physicochemical constituents viz., turbidity, pH, electrical conductivity, total dissolved solids, alkalinity, total hardness, calcium, magnesium, chloride, sulphate, nitrate, fluoride, and iron. The results of the analyses were used to determine the aquifer-wise groundwater quality of the area. The micro-level hydrogeological well inventory was done at 148 locations to have detailed information on the subsurface strata, water levels, aquifer type, and yields, etc.

Based on the existing and additional data generated, various spatial maps on water level, quality, and subsurface lithological sections, which included 2-D, 3-D, and fence diagrams, were prepared. This was followed by the preparation of aquifer maps on a 1:50,000 scale and the formulation of implementable management plans [2].

3. Case study area

Nashik district is one of the six districts of the Khandesh region of Maharashtra state (Latitude: 19°35’N and 20°50’ N; Longitude: 73°16′ E and 74°56′ E). Nashik district is a typical volcanic basaltic area of Maharashtra state, India. Maharashtra state occurs in the western part of India, whereas Nashik district is located in the northwestern part of Maharashtra state (Figure 1). It is the third largest district in Maharashtra in terms of population of 61,09,052 and occupies an area of 15,582 sq km in the north-west part of Maharashtra. The Nashik district, one of the largest districts of the state, has 15 towns/blocks and 1930 villages. Nashik is surrounded by almost 08 districts viz. Dhule, Jalgaon, Aurangabad, Ahmednagar, Thane, and Valsad etc. of Maharashtra and the Navsari and Dangs districts of Gujarat. Thus, eight districts adjoining Nashik form the boundary between Maharashtra and Gujarat. The major part of the district comes under Godavari and Tapi basins. Godavari originates from the Brahmagiri mountain range in the Western Ghats of Nashik district of Maharashtra state [4].

Figure 1.

Index map.

Climate and rainfall play important roles in replenishing groundwater resources, especially the shallow aquifer in such semiarid areas, where rainfall is the primary and main source of recharge. Nashik district experiences a hot tropical climate with extreme summer, mild winter season, and general dryness throughout the year except during the southwest monsoon season, that is. June to September. The rainfall in the district is under the influence of the southwest monsoon. Nashik district falls ‘assured rainfall zone’ under agro climatic zones. The maximum temperature in summer is 42.5°C and the minimum temperature in winter is less than 5.0°C. Relative humidity ranges from 43 to 62%.

Exploratory data			Micro-level HG data acquisaition			Gwmonitoring data			Gwqualitydata
Req.	Exist.	Gap	Req	Exist.	Gap	Req.	Exist.	Gap	Req.	Exist.	Gap
54	14	50	148	0	148	215	85	154	215	85	154

Table 1.

Data gap analysis.

The normal annual rainfall in the district is uneven and varies from 550 mm to 3400 mm (Figure 2). The average rainfall of the district is ≈ 1043.6 mm, spread over 69 rainy days. Igatpuri receives the highest annual rainfall in the district. The presence of both the Western Ghat (hills) and the plateau region, together with the monsoon winds and rugged terrain condition forms the rain shadow zones that result in scanty and deficient rainfall.

Figure 2.

Rainfall distribution.

In the study area, the major part is covered by Deccan Trap basalt aquifers comprising two aquifer systems, whereas alluvium has restricted to only 1500 sq. km. area along the banks of major rivers and considering its limited thickness only one aquifer is established in alluvium.

4. Aquifer system

The entire area of the district is underlain by the basaltic lava flows of the upper Cretaceous to lower Eocene age forming a hard rock aquifer. The shallow alluvial formation of the recent age also occurs as a narrow stretch along the banks of Godavari and Girna Rivers flowing in the area forming a soft rock aquifer.

The groundwater data generated from the monitoring wells, micro-level hydrogeological inventories, exploratory and observation wells, and various thematic layers were utilized to decipher the aquifer disposition of the area. This substantiates information on the aquifer geometry and hydrogeological information about the region where these aquifers occur. In the area, alluvium and Deccan Trap basalt are the only formations. In Deccan Trap basalt, two aquifer systems have been deciphered, whereas in alluvium considering its limited thickness only one aquifer is established (Figure 3) as listed below:

1. Soft Rock Alluvium

   Aquifer – I (Shallow Aquifer): 8 to 32 m

2. Hard Rock Deccan Trap Basalt

   1. Aquifer – I (Shallow Aquifer): 8 to 32 m

   2. Aquifer – II(Deeper Aquifer): 30 to 200 m

Figure 3.

Major aquifers.

The aquifer system characteristics are described in detail in this chapter as the management options mainly depend on these characteristics [1, 2].

4.1 Soft rock aquifer - alluvium

Alluvium occurs in small areas in the form of discontinuous patches along the banks and flood plains of major rivers such as Godavari, Girna, and their tributaries. In alluvium, the granular detrital material, such as sand and gravel, usually occurs as a thin layer in the district that yields water. In the district, alluvium occupies an area of 1500 sq. km consisting of reddish and brownish clays with intercalations of sand, gravel, and Kanker. The loosely cemented coarse sands and gravels form 3–4 meters thick lower most horizons at the bottom of these alluvial pockets. Groundwater in alluvium occurs under unconfined conditions. The dug wells constructed in alluvium are ranging in depth from 8 to 15 m, whereas the borewells range in depth from 15 to 25 m and the yield of both the dug wells and bore wells ranges from 13 to 22 m³/day.

In the alluvium aquifer, the narrow deposits along river courses are observed in the northern part of 15 to 20 m thickness, whereas in the southern part near Godavari River, it is observed in 20 to 25 m depth range with a thickness of granular material being 5 to 8 m (Figure 4).

Figure 4.

Thickness and depth of occurrence of aquifer – I.

4.2 Hard rock aquifer – deccan trap basalt

Basaltic lava flows are normally horizontally disposed over a wide stretch and give rise to a plateau. These flows occur in layered sequences and are represented by a massive unit at the bottom and a vesicular unit at the top of the flow. Flows are separated from each other by a marker bed known as a ‘bole bed,’ which is formed due to weathering of the top part of the flow and represents a hiatus in volcanic activity. The bole beds indicate the change in basaltic flows.

The groundwater in the Deccan Trap occurs mostly in the upper weathered and fractured parts down to 8 to 32 m depth. At places, potential zones are encountered at deeper levels in the form of fractures and inter-flow zones. The upper weathered and fractured parts form a phreatic aquifer and groundwater occurs under water table (unconfined) conditions. The water levels range from 1.2 to 15 m bgl and yield varies from 10 to 100 m³/day depending upon the local hydrogeological conditions. At deeper levels, the groundwater occurs under semi-confined to confined conditions. Borewells drilled down to 200 m depth, tapping weathered, vesicular, and fractured basalt yielded negligible to 2.5 liters per second (lps), whereas the water levels varied from 8 to 55 m bgl.

Deccan basalts are hydrogeologically heterogeneous rocks. The weathered, jointed, and fractured parts of the rock constitute the zone of groundwater storage and flow. The existence of multiple aquifers is characteristic of basalt and is indicative of wide variation in the joint/fracture pattern and intensity. The yield of wells is a function of the permeability and transmissivity of the aquifer, and it depends upon the degree of weathering, the intensity of joints and fractures, and the topographic setting of the aquifer. Due to wide variations in secondary openings, the potential areas for groundwater are generally localized. In general, groundwater occurs under phreatic/unconfined to semi-confined conditions in basalts.

The perusal of the Aquifer-I map (Figure 4) indicates the major part of the shallow basaltic aquifer is observed in the 10 to 15 m range, and the thickness of the aquifer is 8 to 12 m range. The depth of occurrence of 15 to 20 m with 12 to 16 m weathered and jointed thickness in the basaltic aquifer is observed in discontinued patches in the entire district; however, in the western fringe part of the district it is observed prominently and it coincides with highly dissected plateau and denudational slopes. The less than 10 m depth of occurrence is observed in limited and small areas. The Aquifer- I map indicates that a moderate depth of aquifer is available in the major part of the district with sufficient aquifer thickness.

The Aquifer – II is observed only in Deccan Trap basalt formation. The map showing spatial disposition and the vertical extent of Aquifer-II indicating its depth of occurrence and fractured/granular rock thickness has been generated and shown in Figure 5. The Aquifer-II map indicates the deeper basaltic aquifer in the major part (100 m to 140 m range and thickness 1 m to 3 m). The depth of occurrence of 140 to 178 m is observed in the eastern part of the district in Nandgaon and Yeolablocks, in the small central part with 9 to 12 m fractured thickness. The south-western and north-eastern parts of the district are having a shallower depth of occurrence of 30 to 80 m and fractured thickness of 0.50 to 1.00 m in south-western parts and fractured thickness of less than 0.50 m in north-eastern parts of the district. The Aquifer II map indicates that the deeper aquifer depth of occurrence in the major part of the district is 80 to 140 m bgl and the fracture thickness of 1 to 3 m is most vastly spread in the district.

Figure 5.

Thickness and depth of occurrence of aquifer – II.

4.3 Yield potential of aquifer-I and II

The yield potential of the aquifer is the capacity of the aquifer to yield groundwater. The yield potential of Aquifer-I is plotted in Figure 6 and it indicates that in the entire basaltic terrain, the yield is less than 15 m³/day. However, if we correlate the yield potential of Aquifer-I with the depth of occurrence and weathered thickness, it indicates that even though the aquifer occurs down to a moderate depth of 10 to 15 m with a sufficient thickness of 8 to 12 m, and it does not guarantee adequate yield in hard rock basaltic aquifer. Thus, it can be concluded that the yield potential of the basaltic Aquifer - I is independent of aquifer thickness.

Figure 6.

Yield potential of aquifer – I.

The yield potential of Aquifer-II is plotted in Figure 7 and it proves that the major area is characterized by low yields approximately ranging between 0.5 to 1 lps, whereas moderate yields of 1.00 to 1.50 lps are observed in around 25% of the area. In a very small part of Niphad taluka near Godavari River moderate to high yield of 1.50 to 2.50 lps is recorded. However, if we correlate the yield potential of Aquifer-II with a depth of occurrence and fractured thickness, it indicates that even though the aquifer occurs down to moderate to deep depths of 80 to 140 m and is present in a major part of the area, but the yield is not dependent on the depth of occurrence of the aquifer. Thus, the common tendency of the borewell culture of going deep for getting more groundwater is not true in hard rock areas, especially basaltic aquifers.

Figure 7.

Yield potential of aquifer – II.

4.4 3-D aquifer disposition

Based on the existing data, Mapinfo software 8.5 was used to prepare aquifer disposition in 3D, fence diagram, and 3D Lithological disposition diagram, and several hydrogeological sections have been prepared along section lines to understand the subsurface disposition of the aquifer system.

The 3D aquifer disposition is presented in Figure 8, which helps in visualizing the disposition of the aquifers in the three-dimensional model with topographic elevation and drainage. The 3D aquifer fence diagram and the aquifer bar diagram are shown in Figures 9 and 10. Both the fence and bar diagram covers the entire district and they reassert the factual position of the aquifer -I being shallow in depth with less thickness as compared to the aquifer -II. Both these figures also show that the massive part is the most dominant formation in vertical disposition limiting the occurrence of the water-bearing aquifers above it. The fence diagram gives a clear picture regarding the prospective depth of drilling the borewell at any given location in the district.

Figure 8.

3D aquifer disposition.

Figure 9.

Fence diagram.

Figure 10.

Point aquifer disposition by Bar diagram.

4.5 2-D hydrogeological cross section

To study the aquifer disposition in detail, four hydrogeological cross sections indicating aquifer geometry in different directions have been prepared, and the section lines are plotted in Figure 9. These sections indicate the disposition of Aquifers – I and II along with fracture and water levels.

4.5.1 Hydrogeological cross section A-A’

Hydrogeological cross section A-A’ (Figure 11) represents data from seven exploratory wells for 136 km in the N-S direction with the depth of cross section varying from 90 m bgl to 202 m bgl. The thickness of the Aquifer-I is almost uniform along the section line, whereas the Aquifer–II is having more thickness near Washala in the northern part and Kankapur in the central part of the section with the discharge/yield of 8.77 lps at Kankapur. Southwards from Kankapur along the section line, it can be seen that the thickness of Aquifer-II (deeper aquifer) is decreasing. The water levels of Aquifer-I and Aquifer-II have also been depicted in the section and a close observation of the water level indicates that the water table of Aquifer-II is almost the same at Gilane and Shirpurwadi, whereas at other places it is below the water level of Aquifer-I.

Figure 11.

Lithological section AA’.

4.5.2 Hydrogeological cross section B-B′

Hydrogeological cross section B-B′ (Figure 12) represents data from six exploratory wells with a depth of cross section ranging from 180 m bgl to 200 m bgl for 163 km in the W-E direction in the southern part of the district. The thickness of the Aquifer-I is almost uniform along the section line, whereas Aquifer II is having more thickness in the western part up to Sawargaon after which it starts decreasing till Rahudin central-eastern parts. The maximum thickness of Aquifer – II and the maximum number of fractures encountered are observed at Loni in the central part of the section. At Kalkhode, the least number of fractures (1) is encountered, whereas at all other locations, 2 fractures are encountered at various depths. The water levels of Aquifer-I and Aquifer-II have also been depicted in the section and a close observation of the water level indicates that the water table of Aquifer-II is below the water level of Aquifer-I. The water level at Sawargaon in Aquifer-I during the pre-monsoon season was recorded as 7.60 m bgl, whereas in Aquifer-II it was recorded as 13.56 m bgl.

Figure 12.

Lithological section BB’.

4.5.3 Hydrogeological cross section C-C′

Hydrogeological cross section C-C′ (Figure 13) represents data from six exploratory wells with the depth of cross section varying from 190 m bgl to 203 m bgl for 126 km WE direction in the northern part. The thickness of the Aquifer-I and Aquifer–II is less in the western part from Khadakmal to Bhaur, whereas in the eastern part of the section line, both the aquifers are having more thickness from Bhaur to Dapure. At Dapure, a maximum number of fractures are encountered with the discharge/yield of 3.17 lps and at Bhaur, the least number of fractures (1) is encountered with a discharge of 0.14 lps, whereas at all other locations, two fractures are encountered at various depths.

Figure 13.

Lithological section CC’.

4.5.4 Hydrogeological cross section D-D′

Hydrogeological cross section D-D′ (Figure 14) represents data from five exploratory wells with the depth of cross section varying from 156 m bgl to 200 m bgl for 106 km in the NW – SE direction. The thickness of the Aquifer-I is more in the southwestern part and southeastern parts of the section from Khadakmal to Jivhale and from Chapadgaon to Mirgaon. The thickness of Aquifer – II is more in the NW part of the section line from Khadakmal to Jivhale and decreases in the southeastern part of the section near Mirgaon, where discharge/yield of 1.37 lps has been encountered. The massive thicker part in this section indicates the limited thickness of the deeper aquifer.

Figure 14.

Lithological section DD’.

4.6 Pre-monsoon depth to water level (may 2021) of shallow aquifer

The depth to water levels in Nashik district during May 2021 ranges between 0.05 (Trambakeshwar, Trambakeshwar block) and 30.00 m bgl (RavalgaonPz, Malegaon block). The depth to water levels of more than 10 m bgl is observed in mainly Baglan and Kalwan blocks and isolated patches in the remaining parts of the district covering an area of 2118.53 sq. km. The depth to water level between 2 and 5 and 5–10 m bgl is recorded in the major areas of the district covering an area of 12799.4 sq. km. Water level ranges between 0 and 2 m bgl are observed in isolated patches in the Nashik district covering an area of 675.31 sq. km. The pre-monsoon depth to water level map is depicted in Figure 15.

Figure 15.

Pre-monsoon (may 2021) depth to water level of shallow aquifer.

4.7 Post-monsoon depth to water level (Nov 2021) of shallow aquifer

The depth to water levels in Nashik district during November 2021 ranges between ground level (PathareBk, Sinnar block, Chindhi, Dapur, and Nagzari in Malegaon block) and 17.00 m bgl (Chandanpuri, Malegaon block). The depth to water level up to 2 m and 2 to 5 m bgl covers a major part of the district covering an area of around 13890.32 Sq.km. Water level range between 5 to 10 m bgl is observed mainly in Baglan, Deola, and Malegaon blocks and isolated patches in Kalwan, Niphad, Dindori, Sinnar, and Chandwad blocks covering an area of 1487.99 Sq.km.The depth to water levels of more than 10 m bgl are observed in Baglan and Malegaon blocks in the district covering an area of 214.67 Sq.km. The post-monsoon depth to water level map is depicted in Figure 16.

Figure 16.

Post-monsoon (Nov. 2021) depth to water level of shallow aquifer.

4.8 Water level variation between pre-monsoon (may 2021) and post-monsoon (Nov.2021)

The water level variation between the pre-monsoon and the post-monsoon season was also analyzed to study the consequence of the rainfall on the water level scenario. It is noticed that the entire area shows a rise in water levels in the post-monsoon season due to recharge from monsoon rainfall. The minimal water level variation of 0.10 m was observed in various parts of the Baglan, Nandgaon, Niphad, and Trimbakeshwar blocks, while the maximal water level variation of 12.35 m was measured at Visapur, Yevla block. The major part of the area shows the water level variation from 2 to 5 m followed by 5–10 m.

4.9 Pre-monsoon depth to water level (may 2021) of deeper aquifer

Pre-monsoon depth to the water level in Nashik district during May 2021 ranges from 8.76 m bgl (Hingalwadibk, Kalwan block) to 123.5 m bgl (Kaluste, Igatpuri block). The pre-monsoon depth to water level map for Aquifer -II presented in Figure 17 indicates that the depth to the water level of less than 10 m bgl is observed in mainly Surgana, Peth and small isolated patches in Klawan and Dindori blocks covering an area of 626 Sq.km. The major parts of Peth, Dindori, Kalwan, and Baglan blocks and small isolated patches in Yevla, Niphad, Nashik, and Trambakeshwar show depth to water level between 10 and 20 m bgl covering an area of 2855.37 Sq.km. The deeper water level of more than 50 m bgl is observed in major parts of the district in Igatpuri, Sinnar, Nashik, Trambakeshwar, Niphad, Nandgaon, Malegaon, Deola, and Chandwad blocks covering an area of 7097.14 Sq.km. This may be due to the overexploitation of groundwater and it also indicates that the shallow aquifer is not able to sustain the demand; hence, groundwater resources are being also withdrawn from deeper aquifers in this area.

Figure 17.

Pre-monsoon depth to water level of deeper aquifer.

4.10 Post-monsoon depth to water level (Nov 2021) of deeper aquifer

In Aquifer-II, the post-monsoon depth to water level in Nashik district during Nov. 2021 ranges between 3.9 m bgl (Sinnar, Sinnar block) and 71.6 m bgl (Sakore, Nandgaon block). The post-monsoon depth to water level for Aquifer -II is given in Figure 18 and it shows that the depth to water level of less than 10 m bgl has been demarcated in Peth, Surgana, Nashik, Dindori, and parts of Niphad, Sinnar, Kalwan, and Trambakeshwar blocks covering an area of 3647.15 Sq.km. Depth to water level between 10 m bgl to 20 m bgl has been observed in the major part of the district covering an area of 4381.61 Sq.km. Southern parts of the district near Sinnarand eastern parts of the district near Nandgaonshow the deepest water level of more than 50 m bgl covering an area of 2348.13 Sq.km. Deeper water levels between 20 and 50 m bgl are observed in the central-eastern parts of the district near Baglan and Chandvad and also in the south-western parts of the districts.

Figure 18.

Post-monsoon depth to water level of deeper aquifer.

4.11 Water level trend (2012-2021)

The behavior of water level with time gives information on whether water levels are rising or falling with time and the rate of rise and fall. The water level trend is obtained by time series analysis by plotting time on the X-axis and water level on the Y-axis, the trend line is added to the resultant plot, which gives the water level trend for that particular well. Time series analysis helps understand the underlying causes of trends or systemic patterns over time.

During pre-monsoon, a rise in water level trend has been recorded at 105 monitoring wells and it ranges from 0.003 m/year (Padalde, Malegaon block) to 0.99 m/year (Sakore, Kalwan block), while the falling trend was observed in 80 monitoring wells varying from −0.003 (Hatrundi, Surgana block) to −1.49 m/year (Jaidar, Kalwan block). The rising trend of more than 0.2 m/year is observed in parts of the Kalwan, Niphad, and Nasik blocks covering an area of 3456.13 km². The falling trend of more than 0.2 m/year is observed in northern peripheral areas especially east of Surgana and western peripheral areas near Peint covering an area of 2832.01 km² (Figure 19). During post-monsoon, a rise in water level trend has been recorded at 145 stations and it ranges between 0.0006 m/year (PimpalgaonMor, Igatpuri block) and 1.01 m/year (Chirai, Baglan block), while the falling trend was observed in 36 stations varying from 0.0006 (Ankai, Yevla block) to 0.33 m/year (Sakur, Igatpuri block). The rising trend of more than 0.2 m/year is observed near Deola, Kalwan, Chandwad, and Niphad covering an area of 4938.42 km². Whereas a falling trend of more than 0.2 m/year is observed in a limited area of 216.39 km² in the eastern part of Malegaon and the northern part of Igatpuri (Figure 20). The rising water level trend indicates that the groundwater recharge during the period is adequate considering the storage capacity of the aquifer and is more than withdrawal, whereas falling trend indicates that the groundwater withdrawal is more than the recharge.

Figure 19.

Pre-monsoon decadal water level trend (2012-2021).

Figure 20.

Post-monsoon decadal water level trend (2012-2021).

Based on groundwater exploration, depth to water levels, groundwater quality, and aquifer-wise characteristics are given in Table 2 and the major aquifer map is presented in Figure 3.

Type of Aquifer	Aquifer-I; (Hard rock-Deccan Trap Basalt)	Aquifer-I; (Soft Rock -Alluvium)	Aquifer-II; (Hard rock-Deccan Trap Basalt)
Formation	Weathered/Fractured Basalt	Sand Clay Gravel Kankers etc.	Jointed / Fractured Basalt
Depth of Occurrence (m bgl)	8 to 32	8 to 25	30 to 200
Granular/Weathered / Fractured rocks thickness (m	1 to 14	7 to 21	0.5 to 12
SWL (mbgl)	1.40–21.00	5.0 to 10.0	8 to 55
Yield	10 to 100m^3/day	200–300 m^3/day	Up to 3.17 lps
Sustainability	1.0 to 3 hrs	2 to 5 hrs	0.5 to 3 hrs
Transmissivity (m^2/day)	9.25 to 89.04 m^2/day		10.85 to 131.11 m^2/day
Specific Yield/Storativity (Sy/S)	0.019 to 0.028	0.06 to 0.1	1.30 x10^−4 to 5.31 X 10^−5
Suitability for drinking/ irrigation	Suitable for both (except nitrate and fluoride-affected villages for drinking)

Table 2.

Aquifer characteristics of Nashik district.

5. Groundwater resources

5.1 Groundwater resources aquifer-I

Central Ground Water Board and Ground Water Survey and Development Agency (GSDA) have jointly estimated the groundwater resources of Nashik district based on GEC-2015 methodology [5]. The block-wise groundwater resources map is shown in Figure 21.

Figure 21.

Groundwater resources (2020), ashik district.

Groundwater resources estimation was carried out for 15,530 sq. km. area out of which 1650.24 sq. km. is under the command and 11838.32 sq. km. is under non-command, the net annual groundwater availability is assessed as 1849.91 million cubic meters (MCM). The gross draft for all uses is estimated at 1081.66 MCM with the irrigation sector being the major consumer having a draft of 1045.72 MCM. The domestic and industrial water requirements are worked out at 35.94 MCM. The net groundwater availability for future irrigation is estimated at 840.45 MCM (Table 3). Out of 15 talukas, 3 talukas are semi-critical, 6 are critical and the remaining 9 talukas are safe (In India, a taluka is the administrative unit below the district).

Administrative Unit	Net Annual Groundwater Availability	Existing Gross Groundwater Draft for irrigation	Existing Gross Groundwater Draft for domestic and industrial water supply	Existing Gross Groundwater Draft for All uses	Provision for domestic & industrial requirement supply to 2025	Net Groundwater Availability for future irrigation development	Stage of Groundwater Development %	Category
Baglan Satana	121.57	99.05	2.62	101.67	2.62	26.76	83.63	Semi-Critical
Chandwad	109.31	87.32	1.83	89.15	1.83	22.52	81.55	Semi-Critical
Deola	59.83	54.90	1.93	56.83	1.93	8.70	94.98	Critical
Dindori	115.61	65.61	2.55	68.16	2.55	48.23	58.96	Safe
Igatpuri	166.33	39.47	1.97	41.43	1.97	124.89	24.91	Safe
Kalwan	75.68	46.41	1.75	48.16	1.74	27.52	63.63	Safe
Malegaon	181.68	108.16	3.61	111.76	3.61	78.05	61.52	Safe
Nandgaon	98.08	55.30	2.32	57.62	2.32	40.76	58.75	Safe
Nasik	144.41	61.20	1.97	63.17	1.97	82.90	43.74	Safe
Niphad	162.00	154.02	3.75	157.77	3.75	25.10	97.39	Critical
Peth	101.53	3.55	1.75	5.30	1.75	96.23	5.22	Safe
Sinnar	157.84	154.78	2.95	157.73	2.95	22.57	99.93	Critical
Surgana	120.43	12.63	2.10	14.73	2.10	105.70	12.23	Safe
Trambakeshwar	115.10	10.71	2.25	12.95	2.25	102.14	11.26	Safe
Yeola	120.52	92.63	2.60	95.23	2.60	28.36	79.02	Semi-Critical
Total	1849.91	1045.72	35.94	1081.66	35.94	840.45	58.45

Table 3.

Groundwater resources, aquifer-I (shallow aquifer), Nashik district (2020).

5.2 Groundwater resources – aquifer-II

The groundwater resources of the deeper aquifer of the Nashik district were also assessed based on the GEC-2015 methodology. For assessing the resources of Aquifer-II the taluka-wise average thickness of fractured rocks and area occurring under that thickness was deduced from Figure 5. The specific yield (Sy) and storativity (S) values were taken from CGWB pumping tests data, whereas piezometric water level data was generated from exploration data (Table 4). The GEC-2015 methodology suggests the estimation of resources available within the confining layer, as well as those available above the confining layer under hydrostatic pressure [5].

Taluka	Mean thickness of fractured rocks (m)	Area (Sq.km.)	Sy	S	Piezometric head above confining layer (m)	Resource in confining layer (MCM)	Resource above confining layer(MCM)	Total resource (MCM)
1	2	3	4	5	6	7; (= 2*3*4)	8; (= 3*5*6)	9; (= 7 + 8)
Baglan	0.25	440.00	0.005	0.00003	25	0.55	0.33	0.88
Baglan	0.75	425.26	0.009	0.000027	40	2.87	0.46	3.33
Baglan	2.00	463.41	0.007	0.0000012	35	6.49	0.02	6.51
Baglan Total		1328.67				9.91	0.81	10.72
Chandvad	10.50	18.78	0.01	0.000057	35	1.97	0.04	2.01
Chandvad	7.50	110.85	0.01	0.000057	35	8.31	0.22	8.53
Chandvad	0.75	101.47	0.009	0.000027	40	0.68	0.11	0.79
Chandvad	2.00	392.75	0.007	0.0000012	35	5.50	0.02	5.51
Chandvad	4.50	173.37	0.008	0.00001	20	6.24	0.03	6.28
Chandvad Total		797.21				22.71	0.42	23.13
Deola	7.50	79.50	0.01	0.000057	35	5.96	0.16	6.12
Deola	0.75	139.36	0.009	0.000027	40	0.94	0.15	1.09
Deola	2.00	243.04	0.007	0.0000012	35	3.40	0.01	3.41
Deola	4.50	47.51	0.008	0.00001	20	1.71	0.01	1.72
Deola Total		509.40				12.02	0.33	12.34
Dindori	0.75	275.83	0.009	0.000027	40	1.86	0.30	2.16
Dindori	2.00	620.30	0.007	0.0000012	35	8.68	0.03	8.71
Dindori	4.50	7.14	0.008	0.00001	20	0.26	0.00	0.26
Dindori Total		903.27				10.80	0.33	11.13
Igatpuri	0.75	345.95	0.009	0.000027	40	2.34	0.37	2.71
Igatpuri	2.00	316.72	0.007	0.0000012	35	4.43	0.01	4.45
Igatpuri Total		662.67				6.77	0.39	7.16
Kalwan	7.50	25.98	0.01	0.000057	35	1.95	0.05	2.00
Kalwan	2.00	323.67	0.007	0.0000012	35	4.53	0.01	4.54
Kalwan	4.50	261.20	0.008	0.00001	20	9.40	0.05	9.46
Kalwan Total		610.85				15.88	0.12	16.00
Malegaon	0.25	464.51	0.005	0.00003	25	0.58	0.35	0.93
Malegaon	0.75	435.54	0.009	0.000027	40	2.94	0.47	3.41
Malegaon	2.00	685.88	0.007	0.0000012	35	9.60	0.03	9.63
Malegaon Total		1585.93				13.12	0.85	13.97
Nandgaon	0.75	25.03	0.009	0.000027	40	0.17	0.03	0.20
Nandgaon	2.00	1059.39	0.007	0.0000012	35	14.83	0.04	14.88
Nandgaon Total		1084.42				15.00	0.07	15.07
Nashik	0.75	326.31	0.009	0.000027	40	2.20	0.35	2.56
Nashik	2.00	411.02	0.007	0.0000012	35	5.75	0.02	5.77
Nashik Total		737.34				7.96	0.37	8.33
Niphad	10.50	68.62	0.01	0.000057	35	7.21	0.14	7.34
Niphad	7.50	127.46	0.01	0.000057	35	9.56	0.25	9.81
Niphad	0.25	65.19	0.005	0.00003	25	0.08	0.05	0.13
Niphad	0.75	175.28	0.009	0.000027	40	1.18	0.19	1.37
Niphad	2.00	449.20	0.007	0.0000012	35	6.29	0.02	6.31
Niphad	4.50	243.83	0.008	0.00001	20	8.78	0.05	8.83
Niphad Total		1129.57				33.10	0.70	33.79
Peint Total	0.75	496.47	0.009	0.000027	40	3.35	0.54	3.89
Sinnar	7.50	38.61	0.01	0.000057	35	2.90	0.08	2.97
Sinnar	0.25	142.22	0.005	0.00003	25	0.18	0.11	0.28
Sinnar	0.75	557.30	0.009	0.000027	40	3.76	0.60	4.36
Sinnar	2.00	403.00	0.007	0.0000012	35	5.64	0.02	5.66
Sinnar	4.50	126.82	0.008	0.00001	20	4.57	0.03	4.59
Sinnar Total		1267.96				17.04	0.83	17.87
Surgana	0.75	355.74	0.009	0.000027	40	2.40	0.38	2.79
Surgana	2.00	367.43	0.007	0.0000012	35	5.14	0.02	5.16
Surgana Total		723.17				7.55	0.40	7.94
Trimbakesh-war	0.75	424.76	0.009	0.000027	40	2.87	0.46	3.33
Trimbakesh-war	2.00	256.65	0.007	0.0000012	35	3.59	0.01	3.60
Trimbakesh-war Total		681.41				6.46	0.47	6.93
Yevla	0.75	563.22	0.009	0.000027	40	3.80	0.61	4.41
Yevla	2.00	406.05	0.007	0.0000012	35	5.68	0.02	5.70
Yevla	4.50	0.25	0.008	0.00001	20	0.01	0.00	0.01
Yevla Total		969.51				9.50	0.63	10.12
Nashik District Total		25509.68				369.47	13.30	382.77

Table 4.

Groundwater resource assessment of aquifer – II (deeper aquifer).

As per the estimation, the resources in confining layer are 369.47 MCM, whereas resources above confining layer are assessed as 13.30 MCM and the total groundwater resources come to the tune of 382.77 MCM. The net groundwater resources of Aquifer – I are 1849.90 MCM, whereas that of Aquifer-II are only 382.77 MCM, which is about 21% of dynamic resource availability indicating that the deeper groundwater resources are scarce and more vulnerable to overextraction.

6. Groundwater related issues

6.1 Declining water levels

Pre-monsoon groundwater falling trend of more than 0.2 m/year occurs in 2832.01 sq. km of the area in parts of Peth, Surgana, Baglan, Malegaon, Yevla, Igatpuri, Trambakeshwar, Nashik and Nandgaonblocks. Post-monsoon groundwater falling trend of more than 0.2 m/year occurs in 216.39 sq. km of the area in parts of Malegaon, Igatpuri, Nashik, and Baglan blocks.

6.2 Rainfall and droughts

Based on the long-term rainfall analysis from 1998 to 2021, it is observed that Chandwad, Igatpuri, Malegaon, Nashik, Niphad, Peinth, Surgana, Trimbakeshwar, and Yeola blocks experienced declining rainfall trends. Severe droughts have been observed in Trimbakeshwar, Surgana, Sinnar, Peinth, Nandgaon, Malegaon, Kalwan, Igatpuri, Chandwad, and BaglanSatana Blocks at least once, the rest of the blocks never experienced severe drought conditions; however, it has experienced moderate droughts.

6.3 Overexploitation

Three blocks of the district, that is . Deola, Niphad, and Sinnar fall under the critical category and three blocks fall under semi-critical, that is.BaglanSatana, Chandwad, and Yeola and the rest of the blocks are under the safe category in 2020. In critical and semi-critical blocks, a declining groundwater level trend has been observed both in pre-and post-monsoon seasons.

6.4 Low groundwater potential

Groundwater potential areas have been identified in 14,731 sq. km (≈ 90%) in the Nashik district, where yield remains less than 15 m³/day, mostly due to limited depth of weathering and fractures in Aquifer-I (Basalt). Limited aquifer potential of Aquifer-II (Basalt) is observed in about 9390 sq. km (≈59%) area of the district (Yield potential <1.0 LPS). The sustainability of both Aquifers- I & II is, thus, low and the wells normally sustain pumping between less than 1 and 3 hours.

6.5 Cultivation of cash crops

Various cash crops, viz., grapes, onion, pomegranate, and sugarcane, are cultivated in the district, and the major irrigation source is groundwater. This has led to the severe exploitation of groundwater resources in 6 talukas. The water requirement in these crops is also higher as compared to other traditional crops, thus laying more stress on groundwater. Although micro-irrigation techniques are practiced in most areas for the cultivation of grapes, other cash crops are also required to be brought under the ambit of micro-irrigation.

7. Groundwater management plan

The management plan has been proposed to effectively manage groundwater resources and to arrest overexploitation [6]. The management plan comprises two components namely supply-side management and demand-side management. The supply-side management is based on surplus surface water availability and the unsaturated thickness of the aquifer, whereas the demand-side management is by the use of micro-irrigation techniques and changes in cropping pattern. In addition to this, in some parts of the district, groundwater development [7] is also formulated and recommended to authorities for implementation.

7.1 Supply-side management

The supply-side management of groundwater resources can be done through the artificial recharge of surplus runoff available within river subbasins and micro watersheds [8, 9]. Also, it is necessary to understand the unsaturated aquifer volume available for recharge. The unsaturated volume of the aquifer was computed based on the area feasible for recharge, the unsaturated depth < 3 m bgl, and the specific yield of the aquifer. Table 5 gives the block-wise supply-side interventions through recharge structures.

Taluka	Geographical Area	Area identified for AR (sq. km.)	Unsaturated Volume (MCM)	Surplus surface water required for AR (MCM)	Surplus surface water available for AR (MCM)	Proposed number of structures		Total Volume of Water expected to be recharged@ 75% efficiency (MCM)		Total recharge @ 75% efficiency (MCM)
						PT	CD	PT	CD
Baglan Satana	1481.65	883.35	8565.54	11392.17	37.01	97	278	14.58	6.25	20.84
Chandwad	890.07	692.59	1334.27	1774.58	29.02	76	218	11.44	4.90	16.34
Deola	577.46	294.13	2554.73	3397.79	12.32	32	93	4.86	2.08	6.94
Dindori	1141.93	38.88	42.64	56.71	1.63	3	9	0.45	0.19	0.64
Igatpuri	932.97	0	0	0	0.00	0	0	0.00	0.00	0.00
Kalwan	702.96	577.97	4747.58	6314.28	24.22	64	182	9.54	4.09	13.63
Malegaon	1806.39	1186.19	1542.05	2050.92	49.70	108	308	16.19	6.94	23.13
Nandgaon	1164.88	785.76	903.63	1201.82	32.92	63	181	9.49	4.07	13.55
Nasik	846.31	0	0	0	0.00	0	0	0.00	0.00	0.00
Niphad	1151.75	699.99	2187.14	2908.89	29.33	77	220	11.56	4.95	16.51
Peth	715.87	0	0	0	0.00	0	0	0.00	0.00	0.00
Sinnar	1326.48	704.41	2658.77	3536.16	29.51	77	222	11.63	4.98	16.61
Surgana	912.15	0	0	0	0.00	0	0	0.00	0.00	0.00
Trambakeshwar	873.34	0	0	0	0.00	0	0	0.00	0.00	0.00
Yeola	1005.79	471.01	904.46	1202.93	19.74	52	148	7.78	3.33	11.11
Total	15,530	6334.28	25440.80	33836.28	265.41	649	1857	97.51	41.79	139.30

Table 5.

Proposed supply-side intervention through aquifer recharge.

The area identified for recharge measures in the district is worked out at 6334.28 sq.km.; however, in 5 talukas namely Igatpuri, Nasik, Peth, Surgana, and Trambakeshwar, there is no scope for aquifer recharge due to shallow post-monsoon water levels and rising water level trends. The total unsaturated volume available for artificial recharge is 25440.80 MCM, which ranges from 42.64 MCM in Dindorito to 8565.54 MCM in BaglanSatanataluka. Considering 75% efficiency the surface water required will be 33836.28 MCM, whereas the surface water available in the district is only 265.41 MCM, thus there is a huge shortfall of the surface water required for recharging the aquifers. The available surplus surface runoff water can be utilized for aquifer recharge through the construction of percolation tanks, check dams, gabion, underground bandharas, Nala bunds, continues contour trenches (CCT), and other site-specific structures; however, to arrive at specific numbers of the most feasible recharge structures, that is. check dams and percolation tanks were considered. The check dams of 10 TCM capacities with three fillings in a year and percolation tanks of 100 thousand cubic meters (TCM) capacity with two fillings in a year were considered to arrive at the number of the structures. Thus, a total of 649 percolation tanks and 1857 check dams are proposed with the available surface water resources. The tentative locations of these structures are shown in Figure 22.

Figure 22.

Location of proposed aquifer recharge structures.

7.2 Demand-side management

As seen above, supply-side interventions have limitations due to the limited availability of water sources, thereby hindering proper management of the aquifer system. In such cases, it becomes imperative to adopt demand-side interventions and reduce our demand for groundwater by adopting micro-irrigation techniques. Generally speaking, traditional watering methods can lose as much as 50% or even more of the water applied as evaporation and infiltration losses. Whereas, the application of a micro-irrigation system (MIS) can increase yields and decrease water use, fertilizer quantity, and labor requirements [10]. In addition, other indirect benefits, such as significant energy savings, are observed, which are associated with the electricity required to pump water from the aquifer. The MIS system operates under low pressure, and according to the precise water requirement of the crop. Each dripper/emitter supplies a precisely controlled quantity of water and nutrients directly to the root zone of the plant [9, 10].

The demand-side management is proposed in areas where the stage of groundwater development is relatively high and adopting micro-irrigation techniques for water-intensive crops or change in cropping pattern or both are required to save water [9]. In Nasik district, two major cash and water-intensive crops are proposed to be brought under drip irrigation, that is, sugarcane and onion. For sugarcane, the crop water requirement by traditional flooding method is 2.45 m, and by drip irrigation, it is 1.88 m, thus a savings of 0.57 m (23%) can be achieved. Similarly, in the case of onion, the crop water requirement by the traditional flooding method is 0.78 m, and by drip irrigation, it is 0.52 m, thus a savings of 0.26 m (33%) can be achieved. Based on these calculations, the taluka wise demand-side management plan suggested for Nashik district is outlined in Table 6.

Taluka	Geographical Area (Sqkm)	Area proposed to be covered under Drip; (sq. Km)		Volume of Water expected to be saved (MCM). WUE- 0.57 m for sugarcane, 0.26 m for onion		Total water saved (MCM)
		Sugarcane crop area	Onion crop area
Baglan Satana	1481.65	19.03	50.00	10.85	13.00	23.85
Chandwad	890.07	0.11	100.00	0.06	26.00	26.06
Deola	577.46	1.19	100.00	0.68	26.00	26.68
Dindori	1141.93	10.00	10.00	5.70	2.60	8.30
Igatpuri	932.97	2.75	0.00	1.57	0.00	1.57
Kalwan	702.96	7.25	50.00	4.13	13.00	17.13
Malegaon	1806.39	3.58	100.00	2.04	26.00	28.04
Nandgaon	1164.88	2.32	50.00	1.32	13.00	14.32
Nasik	846.31	12.77	0.00	7.28	0.00	7.28
Niphad	1151.75	40.00	100.00	22.80	26.00	48.80
Peth	715.87	0.00	0.00	0.00	0.00	0.00
Sinnar	1326.48	15.00	130.00	8.55	33.80	42.35
Surgana	912.15	0.00	0.00	0.00	0.00	0.00
Trambakeshwar	873.34	0.00	0.00	0.00	0.00	0.00
Yeola	1005.79	2.84	100.00	1.62	26.00	27.62
Total	15,530	116.84	790.00	66.60	205.40	272.00

Table 6.

Area proposed for drip irrigation demand side management.

In Nashik district, an area of 116.84 sq. km. of groundwater irrigated sugarcane crop, and 790 sq. km. of onion crop is proposed to be brought under drip irrigation. The volume of water expected to be saved is estimated at 66.60 MCM for sugarcane and 205.40 MCM for onion, totaling 272 MCM of groundwater savings. The areas of sugarcane and onion, which can be brought under drip irrigation are plotted on the map and presented in Figure 23. If we compare, the groundwater augmentation by aquifer recharge measures is 139.30 MCM; however, water savings by micro-irrigation are much higher at 272 MCM. Thus, demand-side interventions are more beneficial, economical, and suitable for areas where there is limited source water availability for recharge and areas with high groundwater consumption for irrigation, especially cash crops and water-intensivecrops (Figure 24).

Figure 23.

Areas proposed for demand-side interventions.

Figure 24.

Groundwater savings (MCM) due to supply and demand side interventions.

7.3 Expected benefits of aquifer management plan

The impact of groundwater management plans on the groundwater system in the district after its implementation is evaluated, and the outcome shows significant improvement in the groundwater scenario in all blocks (Table 7).

Block	Water expected to be recharged/ conserved by supply-side interventions (MCM)	Groundwater resources after supply-side interventions (MCM)	Improvement in Stage of GWD after supply-side interventions (%)	Water expected to be saved by Demand side interventions (MCM)	Groundwater Extraction after demand-side intervention	Improvement in Stage of GWD after supply-side and demand side interventions (%)	Balance GWR available for GW Development to enhance the stage of GWD is brought to 70% (MCM)	Additional Area (sq.km.) proposed to be brought under assured GW irrigation with av. CWR of 0.65 m after 70% stage of GWD is achieved (sq. Km)
Baglan Satana	20.84	142.41	71.39	23.85	77.82	54.65	21.86	33.63
Chandwad	16.34	125.65	70.95	26.06	63.08	50.21	24.87	38.26
Deola	6.94	66.77	85.11	26.68	30.15	45.16	16.59	25.52
Dindori	0.64	116.24	58.63	8.30	59.86	51.49	21.51	33.10
Igatpuri	0.00	166.33	24.91	1.57	39.87	23.97	76.56	117.79
Kalwan	13.63	89.31	53.92	17.13	31.02	34.74	31.49	48.45
Malegaon	23.13	204.81	54.57	28.04	83.72	40.88	59.65	91.76
Nandgaon	13.55	111.64	51.61	14.32	43.30	38.78	34.85	53.61
Nasik	0.00	144.41	43.74	7.28	55.89	38.70	45.20	69.54
Niphad	16.51	178.51	88.38	48.80	108.97	61.04	15.99	24.60
Peth	0.00	101.53	5.22	0.00	5.30	5.22	65.77	101.18
Sinnar	16.61	174.45	90.41	42.35	115.38	66.14	6.74	10.37
Surgana	0.00	120.43	12.23	0.00	14.73	12.23	69.57	107.03
Trambakeshwar	0.00	115.10	11.26	0.00	12.95	11.26	67.61	104.02
Yeola	11.11	131.62	72.35	27.62	67.61	51.37	24.53	37.73
Total	139.30	1989.21	54.38	272.00	809.66	—	582.79	896.60

Table 7.

Expected benefits after management options.

The total groundwater resource available after supply-side interventions is 1989.21 MCM, whereas the total groundwater draft after the demand-side intervention is 809.66 MCM. Thus, about 582.79 MCM of groundwater is available, which can improve the stage of groundwater development by 17% from 58% to around 41%. With this, an additional area of 896.60 sq. km can be irrigated. The tentative locations of these areas are shown in Figure 25.

Figure 25.

Additional area proposed to be bought under assured GW irrigation.

7.4 Groundwater development plan

As per groundwater resource assessment data of 2020, balance groundwater resources to the tune of 582.79 MCM are available for development ranging from 6.74 MCM in Sinnartaluka to 76.56 MCM in Igatpuritaluka. While proposing a groundwater development plan, it is imperative to consider the shallow aquifer for major groundwater extraction as it gets annually replenished, as well as it is the most promising, sustainable aquifer in the district. Therefore, 90% of these resources are proposed to be developed by 34,967 dug wells tapping shallow Aquifer-I, and the remaining 10% are proposed to be developed by 5828 borewells tapping moderate to deeper Aquifer-II. Thus, about 34,967 dug wells and 5828 borewells can be constructed. The block-wise details are given in Table 8.

Block	Balance GWR available for GW Development after STAGE OF GWD is brought to 70% (MCM)	Proposed No. of DW @1.5 ham for 90% of GWR Available)	Proposed No. of BW @1.0 ham for 10% of GWR Available)	Additional Area (sq.km.) proposed to be brought under assured GW irrigation with av. CWR of 0.65 m after 70% stage of GWD is achieved (sq. Km)
Baglan Satana	21.86	1312	219	33.63
Chandwad	24.87	1492	249	38.26
Deola	16.59	995	166	25.52
Dindori	21.51	1291	215	33.10
Igatpuri	76.56	4594	766	117.79
Kalwan	31.49	1890	315	48.45
Malegaon	59.65	3579	596	91.76
Nandgaon	34.85	2091	348	53.61
Nasik	45.20	2712	452	69.54
Niphad	15.99	959	160	24.60
Peth	65.77	3946	658	101.18
Sinnar	6.74	404	67	10.37
Surgana	69.57	4174	696	107.03
Trambakeshwar	67.61	4057	676	104.02
Yeola	24.53	1472	245	37.73
Total	582.79	34,967	5828	896.60

Table 8.

Blockwise groundwater development plan.

8. Conclusions

The correlation of the yield potential of Aquifer-I with the depth of occurrence and weathered/fractured thickness indicates that even though the aquifer occurs down to the moderate depth of 10–15 m with a sufficient thickness of 8 to 12 m it does not guarantee adequate yield in hard rock basaltic aquifer. Similarly, the correlation of the yield potential of Aquifer-II with the depth of occurrence and fractured thickness also indicates that even though the aquifer occurs down to moderate to deep depths of 80 to 140 m in a major part of the area, the yield is not dependent on the depth of occurrence of the aquifer. Thus, the common tendency of the borewell culture of going deep for getting more groundwater does not hold in hard rock areas, especially in basaltic aquifers.

The deeper water level of more than 50 m bgl is observed in major parts of the district covering an area of 7097.14 Sq.km. This may be due to the overexploitation of groundwater and it also indicates that the shallow aquifer is not able to sustain the demand; hence, groundwater resources are also being withdrawn from deeper aquifers in this area. The net groundwater resources of the aquifer are 1849.90 MCM, whereas that of Aquifer-II are only 382.77 MCM, which is about 21% of dynamic resource availability indicating that the deeper groundwater resources are scarce and more vulnerable to overextraction. Devising a groundwater management strategy or plan for hard rock aquifers is always challenging [7] as compared to alluvium aquifers, which occur in the vast expanses of major alluvial basins of India. This is due to the highly diversified occurrence and considerable variations in the hard rock groundwater availability. The problem is further compounded as in this case, the area has witnessed droughts, declining water levels, and low yield potentials. The multipronged aquifer management plan is suggested for the area, that is. supply-side (augmentation), demand-side (savings), and development side to resolve the issues.

The supply-side interventions, that is. recharge measures in the district are feasible in 6334.28 sq.km.; however in 5 talukas namely Igatpuri, Nasik, Peth, Surgana, and Trambakeshwar, there is no scope for aquifer recharge due to shallow post-monsoon water levels and rising water level trends. However, in patches, these talukas also face water scarcity in the peak summer season. This dichotomy of availability and nonavailability of groundwater concerning the season is very common in hard rock aquifers. The total noncommitted surface runoff required for recharging the aquifers in feasible areas of 6334 sq. km is 33836.28 MCM, whereas the surface water available in the district is only 265.41 MCM, thus there is a huge shortfall of the surface water required for recharging the aquifers. The available surplus surface runoff water can be utilized for aquifer recharge through the construction of 649 percolation tanks, 1857 check dams/gabion, and various other site-specific structures such as underground bandharas, Nala bunds, and CCT (continuous contour trenching).

The demand side interventions, that is., water saving measures are proposed in the areas with the high level of the stage of extraction, an area of 116.84 sq. km. of groundwater irrigated sugarcane crop and 790 sq. km. of onion crop is proposed to be brought under drip irrigation. The volume of water expected to be saved is estimated at 66.60 MCM for sugarcane and 205.40 MCM for onion, totaling 272 MCM of groundwater savings.

If we compare, the supply-side interventions by aquifer recharge measures can augment resources to the tune of 139.30 MCM; however, demand-side interventions by micro-irrigation are much higher @ 272 MCM. Thus, demand-side interventions are more beneficial, economical, and suitable for areas, where there is limited source water availability for recharge and areas with high groundwater consumption for irrigation, especially cash crops and water-intensive crops. The study has indicated that the supply-side interventions have got apparent limitations due to inadequate availability of surplus/noncommitted surface water, as well as the low storage potential of hard rock aquifers.

With supply-side and demand-side interventions, it is expected that about 411 MCM of groundwater would be available to bring down the overall stage of groundwater development of the district from 58.45 to 47.81%. This plan would also address the issue of overextraction in some talukas such as Baglan Satana, Chandwad, Deola, Niphad, Sinnar, and Yeola, where the stage of extraction can be brought down to 70% (safe category).

The management plan provides a scope for the development of available and additional groundwater resources added/saved to the system through the construction of 34,967 dug wells and 5828 borewells in a phased manner in the selected areas. This will provide assured irrigation to an additional area of 896.60 sq. km. The management plan suggested for the area is holistic and implementable with further fine-tuning/inputs at the local scale. It will also lead to the upliftment of the socioeconomic status of the people, especially of those located in tribal pockets of the district. These interventions also need to be supported by capacity building measures, self-regulation, and an institutional framework for participatory groundwater management.