Analysis of supply and demand balance of water resources

Available water resources should be equal to the sum of available surface water resources, available spring water resources and exploitable groundwater.

(1) Available surface water resources

According to the multi-year runoff process of the rivers in Shule River Basin, the surface water resources at all levels calculated by Pearson Ⅲ curve method are shown in Table 10- 1, in which the extreme drought year (P=95%) is13.48 million m3/a and the drought year (P=75%) is/kloc-0. The wet year (P=25%) is16.1000 million m3/a, and the abnormal wet year (P=5%) is 188 million m3/a (table 10- 1).

Table 10- 1 Statistical Table of Annual Runoff of Rivers of Different Levels in Shule River Basin

Available surface water resources refer to the maximum surface water resources cited by existing water conservancy projects (including reservoirs, channels and irrigation stations). There are no water conservancy projects in small gullies such as Annanba River. The water conservancy facilities of Youshi River, Yulin River and Danghe River are relatively perfect, and the cited surface water resources are close to the maximum. After the completion of Changma Reservoir, 64.6% ~ 79.8% of the mountain surface water resources of Shule River can be utilized. According to the calculation, the available surface water resources in the investigation area are11630,000 m3/a(P=75%) and12.09 million m3/a(P=50%), respectively, with the multi-year average of11800,000.

(2) Available spring water resources

Under the current conditions, the spring water resources in the plain area of the river basin corridor are 65.438+560 million m3/a, and the average cited amount for many years is 65.438+200 million m3/a ... It is predicted that after the project is fully implemented, the cited spring water resources at all levels will be 800 million ~ 1. 1 100 million m3/a.

(3) Allowable exploitation of groundwater

According to the calculation results, under the condition of P=50%, the allowable groundwater exploitation in the plain area of river basin corridor is 300 million m3/a.

(4) Available water sources

According to the calculation results of the first three items, the water supply resources in this area are 654.38+55.5 million m3/a(P=75%) and 654.38+64.5 million m3/a(P=50%) respectively, with the multi-year average of 654.38+58 million m3/a (Table 654.38+00-0

Table 10-2 Statistical Table of Available Water Supply in Shule River Basin

(5) Total water resources

The total amount of water resources refers to the sum of surface water resources and groundwater resources that are not repeated with surface water. The surface water resources (average for many years) are1610 million m3/a, and the groundwater resources that are not duplicated with the surface water (including pour point reduction infiltration and flood infiltration) are1250,000 m3/a, and the average for many years is17.35 million m3/a. They are 1.5 times and 2.5 times of the national 2500 m3/ (person a) and Gansu 1.5 m3/ (person a) respectively. Therefore, the Shule River Basin is relatively rich in water resources.

Second, the analysis of water consumption and water consumption structure under current conditions

According to the statistical annual report and actual investigation, agricultural irrigation is the main water resource utilization in Shule River Basin, followed by industrial water and drinking water for people and livestock. In terms of water use, surface water is dominant, supplemented by groundwater.

1999, the total water consumption of all sectors of the national economy in the whole basin was14.49 million m3/a, of which the irrigation water consumption of agriculture and forestry was13.36 million m3/a, accounting for 92.23%, and the industrial water consumption (including the industrial water diversion of 404 factory) was 97 million m3/a, accounting for 6.69%. According to the types of water sources, the river water is11340,000 m3/a, accounting for 78.22%, the spring water is1790,000 m3/a, accounting for 12.34%, and the groundwater is1370,000 m3/a.

In 2004, the total water consumption was 65.438+407 million m3/a, of which the irrigation water consumption for agriculture and forestry was 65.438+309 million m3/a, accounting for 93.0%, the industrial water consumption (including industrial water diversion from 404 factory) was 89 million m3/a, accounting for 6.3%, and the domestic water consumption was 80 million m3/a, accounting for 0.7%. According to the types of water sources, the water diversion amount is 1 1.43 million m3/a, accounting for 8 1.2%, the water diversion amount is 95 million m3/a, accounting for 6.7%, and the groundwater diversion amount is 1.65438+.

Table10-3 Analysis of Water Consumption in Main Irrigation Areas in 2004

Third, the analysis of supply and demand balance

(A) Analysis of supply and demand balance in Shule River project area

Shule River resettlement development project is a key agricultural development project in the Ninth Five-Year Plan and 20 10 long-term planning of Gansu Province. Mid-term adjustment was made in 2002, and the construction period was determined as 10, with 408,000 mu of newly reclaimed land and 75,000 immigrants. Changma Reservoir was completed at the end of 2002 and filled in early 2003, with a storage capacity of 654.38+940 million m3.

After the implementation of the project, the utilization coefficient of canal system in Changma irrigation area, Shuangta irrigation area and Huahai irrigation area is: canal irrigation 0.62, well-canal mixed irrigation area 0.75; The comprehensive net irrigation quota is 365.89m3/ mu in Changma Irrigation Area, 349m3/ mu in Shuangta Irrigation Area and 3 19.94m3/ mu in Huahai Irrigation Area. According to the mid-term adjustment report of Shule River Project, the average irrigation area in the project area (P=50%) is 6.5438+0.622 million mu, and the total water demand is 745.25 million m3/a, of which the drinking water for urban and rural people and livestock is 6.5438+0.110,000 m3. The water demand of township enterprises is 8 million m3; The industrial water demand of Plant 404 is 82.75 million m3; Agricultural irrigation water demand is 632.33 million m3; The irrigation water demand of surrounding forest belt and shelter forest is11160,000m3. After deducting the industrial water from the 404 factory, the total water demand of the three irrigation areas is 662.49 million m3/a, of which the industrial water consumption is 8 million m3/a, accounting for 1.2 1% of the total water demand. Drinking water for people and livestock 1 1 ten thousand m3/a, accounting for1.66% of the total water demand; The water demand for agricultural irrigation is 643.49 million m3/a, accounting for 97. 13% of the total water demand. From the perspective of long-term planning, irrigation water for agriculture and forestry is still a major water user. Among the total water demands of the three irrigation areas, the total water demand of Changma irrigation area is 392 million m3/a, that of agriculture and forestry irrigation is 380.8 million m3/a, and that of drinking water for industry and people and livestock is 1 1.3 million m3/a; The total water demand of Shuangta irrigation area is 6,543.8+0,927,900 m3/a, that of agriculture and forestry irrigation is 6,543.8+0,877,900 m3/a, and that of drinking water for industry and people and livestock is 5 million m3/a; The water demand of Huahai Irrigation Area is 77.7 million m3/a, that of agriculture and forestry irrigation is 74.9 million m3/a, and that of drinking water for industry, people and livestock is 2.6 million m3/a (table 10-4).

Table 10-4 List of Water Demand of Changma, Shuangta, Huahai Irrigation District and 404 Factory

From the comparison table 10-2, it can be seen that the water supply in Shule River project area is11060000 m3 in normal years,10480000 m3 in dry years, and the water demand is 745000000 m3, and the difference between supply and demand is 361000000 m3 and 30 respectively. It can be said that the water supply in the project area meets the water demand. Of course, the above calculation only considers the national economic water consumption, but does not consider the ecological environment water consumption. According to the report "Rational Utilization of Water Resources and Ecological Environment Protection in Hexi Corridor", the ecological water demand of Shule River Basin is 250 million m3/a if only the perfect shelterbelt system and good regional ecological environment are maintained, and the restoration and improvement of degraded vegetation and wind erosion and desertification areas are not considered. In order to maintain a good ecological environment, reduce the sandstorm hazards in existing oases and restore some degraded vegetation, that is, to achieve the goal of improving the ecological environment, the whole basin needs 403 million m3/a of ecological water. Therefore, water consumption for production, life and ecology is basically met in normal years, but there is water shortage in poor harvest years, especially in dry years.

In 2004, the ecological drainage in the project area was 286 million m3/a, of which the ecological drainage in Changma irrigation area was197 million m3/a, that in Shuangta irrigation area was only 66 million m3/a, that in Huahai irrigation area was10.7 million m3/a, and that in Yulin irrigation area was 66 million m3/a.

At present, how to use Changma Reservoir, Shuangta Reservoir and Chijinxia Reservoir to jointly transfer water, so as to basically balance the supply and demand of water resources in Shule River basin and reverse the trend of environmental deterioration is an important topic in the project area.

The water conservancy situation and water resources utilization pattern of Yulin Irrigation Area and Ziqiao Irrigation Area in Yumen-Zhen Shi Basin have not changed obviously, and the supply and demand situation are basically balanced. The total water demand of Yulin irrigation area is 44.37 million m3, including 38.75 million m3 of surface water and 5.62 million m3 of groundwater. The total water demand of Ziqiao Irrigation District is 5.58 million m3, the spring water is 4.68 million m3, and the well water is 900,000 m3. See table 10-5 for the water demand of Yulin irrigation area and table 10-6 for the water supply of Ziqiao irrigation area.

Table 10-5 Water Demand List of Yulin, Ziqiao and Danghe Irrigation Areas

Table 10-6 Water Supply List of Yulin, Ziqiao and Danghe Irrigation Areas

(B) analysis of supply and demand balance in Danghe irrigation area

According to this calculation, the total water demand of irrigation area in normal years is 328.4 million m3, the actual water supply is 303.22 million m3, and the water shortage is 25180,000 m3 (table 10-7).

Table 10-7 Statistics of Water Resources Supply and Demand in Danghe Irrigation Area

By analyzing the supply and demand of water resources with different hydrological data guarantee rates for many years, it is found that the water resources in Danghe Oasis are in short supply, and the balance of supply and demand can only be reached in the wet year. In other years, the supply and demand are in short supply every year, and the gap between supply and demand is large, which is maintained by over-exploitation of groundwater (Table 10-8).

Table 10-8 Analysis of Water Resources Supply and Demand Balance in Different Level Years