Optimization of Groundwater Exploitation in an Irrigation Area in the Arid Upper Peacock River, NW China: Implications for Sustainable Agriculture and Ecology

Abstract

Groundwater is the main irrigation water source in the Upper Peacock River. As fast enlargement of irrigation areas continues in recent years, the groundwater level declines continuously and has posed a threat to the sustainability of local agriculture and ecology. A numerical model was established with the code MODFLOW–2000 in order to predict the declining trend of groundwater level and formulate measures to counter the overexploitation, in which the river–aquifer interaction was elaborated and characterized by field survey. The results show that under current intensity of groundwater withdrawal, the levels of both unconfined and confined waters would decline continuously in 7 years from 2015. To stop the groundwater level from declining on the regional scale, the withdrawal rate should be compressed by 45% with respect to that in 2015. Moreover, taking consideration of the constraint of maintaining the ecological water level in the vicinity of the Euphrates Poplar forest in the study area, the withdrawal rate should be compressed 70% for seven towns around the forest.

Hydrogeochemical Characterization and Its Seasonal Changes of Groundwater Based on Self-Organizing Maps

“…The concentration of SO 4 2− ranged from 6.26 to 1120 mg/L, averaging 82.77 mg/L (higher than the average concentration of Ca 2+ ), indicating possible precipitation or cation-exchange reactions of Ca-bearing minerals or the presence of other sources of SO 4 2− (e.g., mirabilite) in the groundwater runoff. HCO 3 − in most natural groundwater bodies originates from the dissolution of the CO 2 from the atmosphere and the vadose zone and carbonate minerals [3]. The average concentration of HCO 3 − in the groundwater in the study area was 256.74 mg/L.…”

“…Table 1 summarizes the hydrochemical parameters of the groundwater in the study area during the rainy season. The concentration of K + , a basic element required for human health, was overall very low in the groundwater [3], ranging from 0.38 to 9.73 mg/L and averaging at 1.66 mg/L. Overall, there was a strong correlation between the concentrations of Na + and Cl − in the groundwater.…”

“…It calculates the SI for a given mineral under different controlled conditions based on hydrochemical data (Appendix A, Table A1) for the groundwater to reflect the equilibrium state of the mineral. On this basis, the role of one or multiple reactive minerals in controlling the hydrochemical composition of the groundwater can be determined [3,19]. The SI for a mineral can be calculated using Equation ( 4) to determine whether it dissolves or precipitates in the groundwater:…”

“…If the absolute value of the SI falls within 0-0.5, the mineral is considered to be in an equilibrium state. A high absolute value of the SI suggests significant dissolution or precipitation of the mineral [3]. Table 2 summarizes the calculated values of the SI for gypsum, calcite, dolomite, halite, and fluorite.…”

“…Groundwater plays a crucial role in domestic and irrigation activities in arid-semiarid regions where surface water resources are short in supply or low in quality [1][2][3]. Rapid urban and industrial growth has led to overexploitation of groundwater, causing increasingly prominent water-related problems (e.g., depletion of water resources accompanied by groundwater pollution) in local areas [4,5].…”