Formulation and selection of water resources development and utilization scheme

I. Water Resources Development and Utilization Plan

The rational development and utilization scheme of water resources is mainly based on the present situation and existing problems of water resources utilization, taking into account the development and utilization potential of surface water and groundwater, the present situation and development planning of water conservancy, the development conditions of groundwater and other factors. The utilization scheme should be combined with the existing water conservancy engineering measures.

The purpose of formulating the optimal allocation scheme of water resources is to adjust the temporal and spatial distribution of water resources according to the concept of sustainable development, pay equal attention to open source and throttling, utilization and protection, uniformly allocate groundwater and surface water resources, coordinate the contradiction of water use between the upstream and downstream of the whole basin and various regions and departments, and improve the overall water use efficiency. In terms of water demand, through industrial adjustment, we should build a water-saving economy, adjust the layout of productive forces, and curb the growth momentum of water demand to adapt to unfavorable water resources conditions; On the supply side, the use of engineering measures to change the temporal and spatial distribution of water resources is suitable for the production layout and promotes the sustainable development of the economy. The selection of water resources utilization scheme must consider the newly-built and proposed water transfer projects, improve water supply capacity, develop water-saving agriculture, realize the joint utilization of surface water and groundwater, optimize dispatching, improve the utilization rate and benefit of water resources, and achieve the purpose of protecting the ecological environment.

(1) Scheme 1: Water resources utilization scheme of Shule River resettlement project.

This scheme is the water use scheme determined in Shule River agricultural irrigation and resettlement development project, and was put forward under the background that Changma Reservoir was put into operation in 2003 and the joint water transfer of the three reservoirs was realized. Its core content is: agricultural irrigation only uses surface water, industrial water (404 factory water is supplied by surface water) and drinking water for people and livestock is supplied by groundwater, and the water demand of each irrigation area is completely implemented according to the planned amount in Shule River agricultural irrigation and resettlement development project. Specifically divided into: drinking water for urban and rural people and livestock 1 1 10,000 m3 (groundwater recharge); The water demand of township enterprises is 8 million m3 (groundwater recharge); The industrial water demand of Plant 404 is 82.75 million m3 (surface water supply); Agricultural irrigation water demand is 632.33 million m3 (surface water supply); The irrigation water demand of surrounding forest belts and shelterbelts is11160000m3 (surface water supply) (table 10-9).

Table 10-9 Water Resources Utilization Table of Scheme I

Scheme 1: See Figure 10- 1 for the water resources utilization scheme under the conditions of P=50% and P=75%.

It can be seen that when the guarantee rate is P=50% and P=75%, the water supply of each irrigation area can meet the water demand.

The water supply of surface water and groundwater in Yulin Irrigation Area, Ziqiao Irrigation Area and Danghe Irrigation Area remains unchanged, and the water resources utilization scheme is implemented according to the current scheme (Table 10-6, Table 10-7).

(II) Scheme II: A water resources regulation scheme with surface water utilization as the main factor and groundwater as the auxiliary factor.

Because the first scheme only pays attention to the development and utilization of surface water, it pays less attention to the present situation of groundwater development and utilization and the downstream ecological environment water demand. Therefore, the second scheme uses the current groundwater exploitation (agricultural irrigation) as the supplementary source of irrigation water, which increases the groundwater exploitation and reduces the surface water consumption on the basis of the first scheme, and transfers the excess surface water to the natural river channel in the lower reaches of Shule River through the rational allocation of reservoirs, which is conducive to improving or slowing down the deterioration of the downstream ecological environment.

The specific content of the second scheme is that the total water demand of the three irrigation areas is 745.24 million m3, but the supply mode has changed. Drinking water for urban and rural people and livestock 1 1 10,000 m3 (groundwater recharge); The water demand of township enterprises is 8 million m3 (groundwater recharge); The industrial water demand of Plant 404 is 82.75 million m3 (surface water supply); Agricultural irrigation water demand is 632.33 million m3 (including surface water supply of 550.86 million m3 and groundwater supply of 865438+470,000 m3); The irrigation water demand of surrounding forest belt and shelter forest is1160000m3 (surface water supply) (table 10- 10).

Figure 10- 1 Scheme 1: Schematic diagram of water resources utilization in Changma, Shuangta and Huahai irrigation areas.

Table 10- 10 Water Resources Utilization Table of Scheme II

See Figure 10-2 for the seawater resources utilization schemes of Changma, Shuangta and Huahua under the conditions of P=50% and P=75% respectively, and the surface water utilization schemes of Yulin and Danghe irrigation areas are the same as the scheme 1.

(3) Scheme 3: Soil improvement and ecological balance scheme under the rational allocation of surface water and groundwater.

Under the condition that the utilization scheme of surface water and groundwater in Scheme II remains unchanged, all newly reclaimed land in Changma Irrigation Area, Shuangta Irrigation Area and Huahai Irrigation Area will be irrigated with surface water, which will inevitably cause some oasis water levels, especially the newly reclaimed land whose water level is less than 5m, to reach the critical water level (2 ~ 2.5m) for desalting in this basin, leading to secondary salinization. In order to ensure the long-term use of newly reclaimed land, drainage and salt washing measures must be taken in areas where the annual water level is less than 2 m. Although horizontal drainage and salt washing measures have been taken in the canal system, according to the previous experience of soil improvement, this measure alone cannot achieve the expected effect, and vertical drainage must be adopted. Using shaft drainage can not only reduce its water level to be higher than the critical backwater level of the basin, but also avoid secondary salinization, which is beneficial to the combination of well irrigation, make full use of water resources, save more ecological water for the fragile ecological environment in this area, and kill two birds with one stone.

Under the condition that the total water demand of Shuangta Irrigation District, Changma Irrigation District and Shuangta Irrigation District remains unchanged, some newly reclaimed land with water level less than 5m adopts well irrigation and well drainage project, which improves saline soil and increases the groundwater exploitation amount of agricultural irrigation, so that the groundwater exploitation amount of Huahai Irrigation District, Changma Irrigation District and Shuangta Irrigation District increases to 6,543,800 m3, 53,460 m3 and 6,543,838+382,000 m3 respectively on the basis of the original exploitation amount.

The specific content of the third scheme is that the total water demand of the three irrigation areas is 745.24 million m3. Drinking water for urban and rural people and livestock 1 1 10,000 m3 (groundwater recharge); The water demand of township enterprises is 8 million m3 (groundwater recharge); The industrial water demand of Plant 404 is 82.75 million m3 (surface water supply); Agricultural irrigation water demand is 632.33 million m3 (including surface water supply of 477.43 million m3 and groundwater supply of154.9 million m3); The irrigation water demand of surrounding forest belt and shelter forest is1160000m3 (surface water supply) (table10-1).

Table 10- 1 1 Water Resources Utilization Table of Shulehe Project Area (Scheme III)

Water resources utilization schemes with guarantee rates of P=50% and P=75% respectively (see figure 10-3). The water resources utilization scheme of Yulin and Ziqiao is the same as the scheme 1.

Figure 10-2 Scheme 2: Schematic diagram of water resources utilization in Changma, Shuangta and Huahai irrigation areas.

Figure 10-3 Scheme III: Schematic diagram of water resources utilization in Changma, Shuangta and Huahai irrigation areas.

Agricultural water-saving measures such as drip irrigation, sprinkler irrigation and changing crop planting structure were adopted in Danghe irrigation area to reduce irrigation quota and the number of agricultural mining wells. Irrigation quota is reduced from the current 660m3/ mu to 560m3/ mu, and 327,000 mu of cultivated land can save 32.7 million m3/a of groundwater. The supply and demand situation is close to equilibrium. See table 10- 12 for the water supply scheme of this irrigation area.

Table 10- 12 Water Resources Allocation Scheme for Danghe Irrigation Area (Scheme III)

Second, the balance analysis of water resources supply and demand in each scheme

See table 10- 13 for the supply and demand balance of each scheme in Shule River project area. It can be seen that the water supply can meet the water demand under different schemes with guarantee rates of P=50% and P=75%, but the supply structure has changed. Scheme 1: Agricultural irrigation water is supplied by surface water, and industrial and human and animal water is supplied by groundwater; In the second and third schemes, agricultural irrigation water is replenished by surface water and groundwater, while industrial and human and animal water is still replenished by groundwater, which also provides more ecological water for the ecological environment in this area. When the guarantee rate is P=50%, the water supply under different schemes not only meets the drinking water needs of industry, agriculture and people and livestock, but also the total amount of abandoned water and ecological drainage in each irrigation area is more than 250 million m3/a, which provides the ecological water consumption for maintaining the current ecological environment (according to the Report on Rational Utilization of Water Resources and Ecological Environment Protection in Hexi Corridor, the ecological water consumption for maintaining the current ecological environment in Shule River Basin is 250 million m3/a). When the guarantee rate is P=75%, three different schemes can give priority to meeting the drinking water demand of industry, agriculture and people and livestock. However, considering the eco-environmental water demand, the abandoned water and ecological drainage of Scheme I and Scheme II are1930,000 m3/a and1853,000 m3/a, respectively, which cannot meet the ecological water demand. Only the abandoned water and ecological drainage of Scheme III are 2,665,438. It can be seen that adopting scientific and reasonable optimal allocation under different schemes and uniformly allocating surface water and groundwater resources in the whole basin can meet the requirements of sustainable economic development and maintaining the current ecological environment in this area.

Table 10- 13 Analysis Table of Supply and Demand Balance in Changma, Shuangta and Huahai Irrigation Areas with P=50% and P=75% guarantee rates.

sequential

For Danghe Irrigation District, it can be seen from the current situation of water use that agricultural water is not only a big user, but also wastes a lot of water resources, which is mainly manifested in the large actual irrigation quota of agriculture, the low utilization rate of canal system, and the ecological environment deterioration problems such as groundwater table decline, crescent moon spring shrinkage, and downstream river cut-off. Therefore, agriculture in this area should vigorously promote water-saving irrigation, improve the utilization rate of water resources, reduce the amount of groundwater exploitation, and slow down or prevent further deterioration of the ecological environment. Scheme 1, Scheme 2 mainly uses water at present, and Scheme 3 mainly uses water after saving water, that is, reducing the irrigation quota 100 m3/ mu in Danghe irrigation area can reduce the groundwater exploitation by 30 million m3/a, meet the allowable exploitation of irrigation area by about 45.56 million m3/a, and basically balance the supply and demand of water resources.