Water Use in the Khanka Lake Basin – Modern and Future Estimations

Abstract

An assessment of the current use of water resources in the Khanka Lake basin is given. It has been established that in the Russian and Chinese territories of the Khanka Lake basin, the use of water resources is determined by the predominant development of agriculture. On the basis of actual and expertly calculated data, the volumes of water use for the entire period of economic activity in the Russian part of the lake basin have been restored. It has been established that the waters of the lake are the source for irrigation of rice crops in Russia, the use of the waters of Lake Khanka in China is possible only in dry years. From the territory of China, in high-water years, the discharge of flood waters of the Mulinghe River into Lake Malaya Khanka and, from it through the hydraulic structures (HS) into Lake Khanka, can have a significant impact on the increase in the water level in the lake. In accordance with the plans for the development of the agricultural sector of the economy of the Lake Khanka basin, scenarios for the development of water consumption in the Russian territory of the Lake Khanka basin until 2030 are considered.

1. Introduction

Since 2010, the water level in Lake Khanka has been constantly rising, which leads to the flooding of coastal, including populated, territories. In recent years, many Russian scientists have been identifying the causes of the extreme increase in the water level in the lake.

The change in the water level (volumes) of Lake Khanka depends on the ratio of water inflow to the lake and its consumption, which in turn are determined by hydrometeorological factors in its basin as well as factors of anthropogenic activity. Unfortunately, studies of the hydrological regime and water balance of the lake have not been carried out since the early 1980s. The latest fundamental studies of the lake were carried out by M. G. Vaskovsky, published in his monograph The Hydrological Regime of Lake Khanka in 1978.

One of the anthropogenic factors affecting the change in hydrological characteristics is water use. The purpose of this work is to study the influence of anthropogenic factors on the water level associated with the use of irrigation lands and water resources of Lake Khanka. The main tasks in achieving this goal are to determine the structure of the current use of water resources and the volume of water withdrawal for economic needs in the Russian and Chinese parts of the transboundary catchment area of Lake Khanka based on official statistical information and expert assessments. The assessment of these values was made for the first time and allows us to conclude that the impact of water use on the change in the water level in the lake is minimal.

2. Methods

2.1 Description of the study site

Lake Khanka, the largest lake in the Far East, belongs to the drainage basin of the Amur River and is located on the border of the Primorsky Territory of the Russian Federation (Ozero Khanka) and the Heilongjiang Province of the People’s Republic of China (Khanka Lake) (Figure 1) [1].

Figure 1.

Scheme of Lake Khanka.

The total area of the water surface of Lake Khanka at an average long-term level of 68.90 m BS is 4070 km², including within Russia (3030 km²)—excluding Lake Small Khanka, as well as lakes-lagoons Trostnikovoe (area 22.8 km²), Protoka (5.37 km²), and Krylovo (1.35 km²). The total area of these lagoon lakes, connected to Lake Khanka by channels (straits), is 29.5 km², or only 0.7% of the lake area.

The surface area of the lake is not constant; it varies depending on the level from 3940 to 5010 km². The volume of the water mass of the lake at a level of 68.90 BS is 18.3 km³, varying depending on the level from 12.7 to 22.6 km³. In plan, the lake is pear-shaped, with the largest expansion in the northern part. The maximum length of the lake is 90 km, and the maximum width is 67 km [2].

There are 15 river streams flowing into the lake from the Russian territory and 9 from the Chinese side.

The Sungach River is the only natural watercourse through which the flow from Lake Khanka is carried out. The river flows out of the northeastern part of the lake and flows into the Ussuri River 450 km from its mouth through a heavily swampy lowland near Sungachen [2].

On the coast of Lake Khanka, as well as in the upper and middle reaches of the Sungach River, there is the Khanka State Natural Reserve, established in 1990. Since 2005, the Khanka State Nature Reserve has been awarded the international status of a UNESCO Biosphere Reserve. On the one hand, Lake Khanka and the surrounding wetlands of the reserve are an object of not only national but also international importance, which was the first in the Far East to be included in the list of wetlands of the Ramsar Convention as a habitat for waterfowl. On the other hand, the Khanka Lake basin is one of the main areas of agriculture in the Far East of Russia, the active economic development of which in the second half of the 20th century led to a significant transformation of landscape complexes, pollution of the aquatic environment and soils, and a change in the hydrological regime of the rivers of the basin and Lake Khanka itself. During the long economic crisis of the 1990s in the basin of Lake Khanka, there was a significant decrease in agricultural pressure. However, since the early 2000s, in both the Russian and Chinese parts of the lake basin, there has been an increase in economic activity, which indicates an increase in anthropogenic pressure in the transboundary basin as a whole.

2.2 Data sources and analysis

Given that the only anthropogenic factor affecting the state of the lake is agriculture, namely, rice cultivation, the water resources of the Khanka Lake basin are used mainly for the development of rice cultivation.

To assess the current state of water use and the long-term dynamics of water withdrawal and water consumption in the Khanka Lake basin, the data of direct accounting of water intakes and discharges in the lake basin for the period 1985–2015 were summarized and analyzed. Data of direct recording of water intakes and discharges in the lake basin for the period 1985–2015 were provided by the Amur Basin Water Administration in the framework of the project to study the hydrological features of the water regime of Lake Khanka in order to identify the causes of the abnormal rise in the water level (the author of this chapter is a participant in this project). Currently, the volume of water use for all economic needs or water withdrawal in the basin of Lake Khanka is 156.2 million m³ per year, and the volume of discharge is 53.4 million m³ per year. Of the total volume of water use, water withdrawal for irrigation—flooding of rice fields—makes up almost the entire volume of water used in the basin—more than 90%. At the same time, the volumes of water for industrial and communal needs (household and drinking) are approximately the same. Water withdrawal directly from the lake for irrigation is about 95%; the rest of the water is taken from rivers within the lake basin. Water losses or water consumption in the basin of Lake Khanka is 102.8 million m³ per year, reaching up to 70% of total water withdrawal in some years.

The dynamics of the areas of irrigated land in the basin of Lake Khanka for 1995–2015 was established on the basis of officially provided data by the administration of melioration and agricultural water supply in the Primorsky and Khabarovsk territories (Primmeliovodkhoz) as part of the implementation of the above scientific project.

The availability of actual data and calculated data on irrigated areas for the entire long-term period, as well as the values of water consumption calculated from the difference between water withdrawal and discharge in those years when official accounting information was available for them, made it possible to restore the volumes of water use and water consumption for the entire period of economic activity in the lake basin. An analysis of all available data showed that irretrievable losses per hectare of irrigated land can range from 7000 to 9000 m³ per year.

The selected time period (1960–2015) makes it possible to assess the long-term dynamics of water use and irrigated areas and assess the impact of irrigation on the water regime of Lake Khanka at various stages of the economic use of land and water resources in the basin under study.

The actual and expertly determined values of water withdrawal and water consumption in the basin of Lake Khanka for the entire period of irrigated agriculture are shown in Figure 2 [3].

Figure 2.

Long-year dynamics of water use in the Lake Khanka basin during the period from 1960 to 2015.

As it follows from the figure, the maximum volumes of water required for irrigation were in the mid-1980s. By 1985, the total water consumption reached more than 600 million m³ per year.

The minimum values of water use were noted in the period 2002–2007, when rice cultivation was stopped in the lake basin, which consumes the main volume of water taken from Lake Khanka.

Restoration of rice cultivation began in 2008, which immediately affected the increase in total water withdrawal. By 2012, water use increased to 292 million m³; then, in 2013–2015, a slight decline in water withdrawal followed, which was due to a decrease in rice crops during this period.

For the entire period of economic activity under consideration, water consumption also varied widely from 40 to 385 million m³ per year. The highest values of irretrievable losses fall on the years of the greatest development of irrigated agriculture in the basin of Lake Khanka.

Comparison of the values of irrigated lands and water consumption for the period 1960–2015, necessary for assessing the water balance of the lake and the impact of irrigation on the water resources of Lake Khanka, is presented in Table 1.

Year	Irrigated lands, ha	Water consumption, million m^3 per year	Year	Irrigated, ha	Water consumption million m^3 per year
1960	2700	19.6	1988	40,300	274.8
1961	3200	23.1	1989	36,300	239.2
1962	3700	26.6	1990	32,300	251.3
1963	4200	40.0	1991	28,700	210.1
1964	4700	44.1	1992	29,600	237.0
1965	5200	43.2	1993	28,700	267.5
1966	6400	57.6	1994	14,300	201.5
1967	6900	62.1	1995	10,400	124.4
1968	7900	63.2	1996	7500	85.1
1969	9800	88.2	1997	3000	74.4
1970	11,800	94.4	1998	4800	38.7
1971	13,700	108.8	1999	5000	76.2
1972	14,900	134.1	2000	6100	94.0
1973	16,300	146.7	2001	7500	111.2
1974	18,800	169.2	2002	6900	36.52
1975	20,900	188.1	2003	4600	51.62
1976	22,600	203.4	2004	1900	11.78
1977	25,800	206.4	2005	2800	16.8
1978	28,600	228.8	2006	3300	22.38
1979	31,100	248.8	2007	4800	22.4
1980	34,700	277.6	2008	7000	70.31
1981	35,100	280.8	2009	16,100	172.8
1982	36,200	289.6	2010	21,300	200.2
1983	39,300	314.4	2011	22,400	198.1
1984	41,100	328.8	2012	23,300	205.8
1985	52,200	384.6	2013	19,800	155.2
1986	48,200	284.7	2014	22,500	152.5
1987	44,200	324.0	2015	19,600	127.3

Table 1.

Irrigated areas and water consumption in the basin of Lake Khanka for the period 1960–2015.

According to [4], a distinctive feature of land use in the Chinese part of the Khanka basin is the high proportion of rice fields and arable land, which in total makes up 44.4% of the territory. At the same time, the area of rice fields is 2.2 times larger than that of the arable land occupied by other agricultural crops.

The data published by the Chinese side on water management infrastructure and water use in the Chinese territory of the basin are very incomplete and contradictory. An assessment of the water management situation in the Chinese territory of the lake basin was carried out using satellite data as part of a scientific project to study the rise in the water level in Lake Khanka and materials of the Joint Russian-Chinese Commission on the Rational Use and Protection of Transboundary Waters (June 2016) [2].

Since the late 1990s, a large-scale integrated water management system has been created in the Chinese part of the Khanka Lake basin, including HS, irrigation and reclamation canals, runoff diversion channels, and large irrigation systems, mainly rice ones. The main purpose of the water management system of the People’s Republic of China in the basins of lakes Khanka, Small Khanka, and the Mulinghe River is to provide water for rice irrigation systems (RIS) and redistribute flood waters.

The Chinese part of the catchment area of Lake Khanka, including Lake Small Khanka, is relatively small, and economic activity on it cannot have a significant impact on the water regime and water balance of Lake Khanka. The main influence here belongs to the transfer of runoff from the Mulinghe River, which can then both enter Lake Khanka and, bypassing it, be fed to the RIS and discharged into the Sungach River.

The water management system in the Chinese territory of the Khanka Lake basin consists of the components shown in Figure 3 (based on the Landsat 8 satellite image, May 2016) [2]:

1. Water divider on the Mulinghe River;

2. Dongdihe Canal (Musin);

3. Distribution reservoir;

4. Two discharge channels diverting water from the reservoir to the RIS and to the Sungach River;

5. Lake Small Khanka;

6. Three HS on the isthmus between the lakes Small Khanka and Khanka.

Figure 3.

The water management system in the Chinese side.

Lake Small Khanka serves as a storage reservoir for water supply to the RIS.

At the same time, the presence of spillways with a total capacity of up to 200 m³/s indicates that the Chinese side is designed to discharge the flood waters of the Mulinghe River, since Lake Small Khanka’s own catchment area is very small and the flow from it cannot reach such values.

In conditions of medium water content, the runoff taken from the Mulinghe River in the amount of about 700 million m³ per year is completely spent on the needs of rice cultivation. This value is estimated based on the irrigation norm of rice 700 m³ per year per 1 mu (author’s note 666.7 m²). This volume may not affect the balance of Lake Khanka, since discharges from irrigated areas are carried out mainly into the Sungach River, and additional injection from Lake Khanka is not carried out.

With a reduced water content of the Mulinghe River, it can be assumed that the river’s own water resources will not be enough to cover the irrigation needs of the RIS, as a result of which water can be taken from Lake Khanka to Lake Small Khanka using pumping stations, the maximum capacity of which after reconstruction will be increased to 100 m³/s.

In high-water years, an increased flow of water enters the Dongdihe (Musin) canal from the Mulinghe River, and the lock-regulator on the Mulinghe River limits the flow of the river below the canal, while the flow into the canal itself is not regulated. In order to avoid flooding of irrigated fields and residential areas, all excess water is probably discharged into Lake Small Khanka, and from there, through the waste hydraulic structures, into Lake Khanka. As noted above, the discharge value can reach 200 m³/s. This is a design value that has a low probability. However, if we assume that during the high-water period 100 m³/s will be discharged into Lake Khanka, then for 4 months of operation of spillways, an additional 1 km³ of water will enter the lake, which may affect the level regime of the lake.

During the period under review, there is a gradual increase (with fluctuations) in total rice crops from 33,000 hectares in 1976 to 115,000 hectares in 2015. At the same time, the contribution to the development of irrigated agriculture in the study basin from the Russian Federation and China turned out to be different both in time and in magnitude. Until 1994, the area under rice cultivation in Russia exceeded that in China. In some years, Russia’s contribution even reached 95%. However, since 1995, China has taken the lead in rice cultivation, and by 2004, the Russian Federation accounted for only 3% of the total area under rice in this basin. Only since the end of the first decade of this century, in connection with the revival of rice cultivation in Russia, has its contribution increased in recent years to 18% [3].

In addition to the noted differences in the areas under rice cultivation and trends in their changes, the sources of water for irrigation also differ. In the Russian part of the basin, the waters of the lake serve as a water source, and an increase in rice crops can lead to a decrease in the level due to water consumption. It should be noted that such a decrease, even during the period of maximum development of rice cultivation, did not exceed 10 cm. Irrigation water in the Chinese part of the basin is mainly supplied by the flow of the Mulinghe River. The use of the waters of Lake Khanka in China is possible only in dry years, which may lead to a decrease in its level. And, vice versa, in the years of increased water content in the Mulinghe River basin, through the network of canals, excess flood runoff of this river is discharged into Lake Small Khanka, and from it into a large lake, with a subsequent possible increase in the water level in it [3].

2.3 Scenarios for the development of agriculture and water use in the Russian territory of the Khanka Lake basin until 2030

An analysis of economic activity in the Khanka Lake basin showed that the main anthropogenic factor in the lake basin is irrigated agriculture, which requires large amounts of water. The volume of water withdrawn from the lake and, accordingly, water consumption in the lake basin directly depends on the prospective development of this industry. To develop scenarios for the development of such a water-intensive sector of the economy as irrigated agriculture, the existing national plans for the development of the agro-industrial complex of Russia [5, 6] and regional plans for the development of Primorsky Territory, a constituent entity of the Russian Federation, on the territory of which the Lake Khanka basin is located, were analyzed [7].

Based on all available information, three scenarios for the development of irrigated agriculture in the Khanka Lake basin up to 2030 are proposed.

The first scenario—the crisis one—is based on the premise that there will be no further increase in irrigation in the lake basin and that the areas under rice crops will remain unchanged until 2030.

In the second scenario—inertial—with the expansion of rice crops, it is planned to restore over 80% of the existing reclamation fund.

In the third scenario—the innovative one—the growth of irrigated lands is allowed due to the involvement in agricultural turnover of new plots located beyond the currently existing border of irrigation-developed territories. That is, it is supposed to fully develop all available irrigation-prepared irrigated lands in the basin under consideration.

To assess long-term plans for the state of irrigation and, consequently, irretrievable losses in the basin of Lake Khanka, the indicators given in [5, 6, 7] were taken into account and methodological approaches developed earlier at the State Hydrological Institute were applied in assessing irretrievable water consumption losses in irrigated agriculture [8].

For the initial level of rice cultivation, the average value for 2010–2015 was taken, the period of relatively stable irrigated land in the Khanka Lake basin, which is 21,500 hectares. During this period, the share of irrigated lands in the basin of Lake Khanka was estimated at 87% of all irrigated lands in Primorsky Territory. This ratio was adopted when calculating the prospective values of rice crops.

The following assumptions and norms were adopted to estimate the values of irretrievable losses from irrigated areas.

For the crisis scenario, according to which no further increase in irrigation in the lake basin and areas under rice until 2030 is expected, the calculation is made taking into account the current indicators of irretrievable water consumption, when water consumption from one hectare of irrigated land ranges from 7000 to 9000 m³ per year (irrigation period). This value was obtained on the basis of available official information on water withdrawals and discharges in the lake basin in recent years.

For the inertial and innovative scenarios, the irrigation norms recommended for this region for rice, which range from 10,000 to 12,000 m³/ha, are taken for calculation [9]. The value of 12,000 m³/ha seems realistic for the inertial scenario in the case of expansion of rice crops and simultaneous reconstruction of rice irrigation systems through government programs and foreign and private investments in the development of rice cultivation in this region. An irrigation norm of 10,000 m³/ha is included in the forecast for the period up to 2030 under the innovative scenario, taking into account the modernized irrigation system with lower losses during water transportation through irrigation canals.

The annual values of rice planting areas and water consumption in the Khanka Lake basin under three scenarios until 2030 are shown in Table 2.

Year	Scenarios
	Crisis		Inertial		Innovative
	Irrigated land	Water consumption	Irrigated land	Water consumption	Irrigated land	Water consumption
2010–2015	21,5	173	21,5	173	21,5	173
2024	21,5	173	35,0	350	43,2	432
2025	21,5	173	36,8	368	46,1	461
2026	21,5	173	38,7	387	48,9	489
2027	21,5	173	40,5	405	50,0	500
2028	21,5	173	42,4	424	52,4	524
2029	21,5	173	44,2	442	54,2	542
2030	21,5	173	46,1	461	55,0	550

Table 2.

Annual values of promising rice crops (thousand hectares) and volumes of water consumption (million m³ per year) in the Khanka Lake basin.

Thus, in accordance with the three proposed scenarios for the development of irrigated agriculture in the Khanka Lake basin, the size of rice cultivation remains at the current level—about 22,000 hectares (crisis scenario) and increases to 46,000 hectares (inertial scenario) or up to 55,000 hectares (innovative scenario). At the same time, water consumption can be up to 200 million m³ per year, more than 450 million m³ per year and 550 million m³ per year, respectively, according to the crisis, inertial, and innovative scenarios.

3. Conclusion

In the whole complex of the anthropogenic factors on the Russian part of the Lake Khanka basin, water use for irrigation is a principal factor. To quantify the impact of economic activity in the lake basin on the long-term dynamics of its level, the dynamics of water consumption was estimated for the entire period of development of rice cultivation in the lake basin—from the 1960s. It has been established that water consumption in different years here is up to 70% of the total water withdrawal.

The highest values of water consumption fall on the years of maximum development of irrigated agriculture in the basin of the Lake Khanka. During these years, water consumption reduced the water level by up to 10 cm for the period 1975–1994.

In modern conditions, when irrigation in the basin of the Lake Khanka has decreased by almost 3 times compared to the 1980s, the impact of the anthropogenic factor from the Russian part of the basin on the lake level regime can be neglected.

In the Chinese part of the basin, irrigation is also the dominant factor influencing the regime of the Small Khanka Lake and the Lake Khanka.

Assessment of the impact of the diversion scheme and the use of the Mulinghe river runoff to the basin of the Lake Khanka leads to the conclusion that Small Khanka Lake acts as a storage reservoir for the water use of the RIS. At the same time, the presence of spillways on the isthmus of Small Khanka Lake–Lake Khanka with a total capacity of up to 200 m³/s indicates that the Chinese side is designed to discharge the flood waters of the Mulinghe River.

In accordance with the three proposed scenarios for the development of irrigated agriculture in the basin of Lake Khanka, the values of water consumption in the basin for the period up to 2030 were obtained depending on the size of rice cultivation. The lowest values of water consumption up to 200 million m³ per year will be the case if the irrigated areas remain at the current level—about 22,000 hectares (crisis scenario). Water consumption of more than 450 million m³ per year may occur with an increase in irrigated land to 46,000 hectares (inertial scenario). The maximum values of water consumption of about 550 million m³ per year are possible in the implementation of the innovative scenario, in which all available irrigation-prepared lands will be developed—55,000 hectares in the Lake Khanka basin.