Abstract
Along with the growth of the population and economic and social development, water consumption in the upper-middle reaches of inland rivers is increasing, which has resulted in long-term cutout in the lower reaches of the river, shrinkage and drying up of the wetlands around the terminal lakes, and has caused a series of ecological problems at the same time. In order to protect the fragile ecological environment, comprehensive harnessing projects have been carried out in many inland river basins in China, in which adopting ecological water conveyance to rehabilitate degraded terminal lakes and wetlands is an important means. From June 2014 to October 2017, the water in the upper-middle reaches of the Shiyang River Basin and the lake water of the terminal lake after ecological water conveyance was sampled. The effects of ecological water conveyance on the characteristics of surface water and groundwater were analyzed using, for example, the Piper triangle diagram, Gibbs boomerang envelope model, and mixing diagram. After ecological water conveyance, the ion concentration of water in Qingtu Lake was higher overall, and ion concentration of water in the unstable catchment was higher than that of the stable catchment. The time variation was characterized as high in the summer half year and low in the winter half year. The water of Qingtu Lake is of high and large salinity, and its hydrochemical type is Na–SO4 (Cl), which is obviously different from the water in the middle-upper reaches of the Shiyang River Basin. The effects of silicate weathering and evaporation crystallization are the main factors leading to the high ion concentration in the water of Qingtu Lake. Ecological water conveyance and the strong evaporation of arid areas have intensified the salinization of water and soils in Qingtu Lake. Meanwhile, implementing the ecological water conveyance policy in the terminal lake has also led to shortage of water resources for agricultural irrigation in the middle reaches of the Shiyang River Basin. The serial negative ecological effects of the ecological water conveyance should be emphasized.
Highlights
As a relatively closed water circulation system, the characteristics and evolution mechanism of terminal lakes are similar and different from those of rivers [1,2]
The results showed that the water in Qingtu Lake was weak alkaline, with an average pH value of 8.18 and a range of 7.19 to 9.14; the average SAL was 10.84 ppt, and the variation range was between 0.2 and 60 ppt; the average total electrical solid solubility (TDS) of the water samples in the range of instrument detection was 19,749.14 mg L−1, and the variation range was 614 to 97,400 mg L−1, and the TDS of some samples exceeded the instrument monitoring limit of
The average TDS of Qingtu Lake was above 50,000 mg L−1
Summary
As a relatively closed water circulation system, the characteristics and evolution mechanism of terminal lakes are similar and different from those of rivers [1,2]. Water 2019, 11, 1673 characteristics of surface and groundwater around lakes [5,6,7]. The ecological water conveyance project is an important way of water resource regulation, which is widely used in arid and semiarid areas, such as Central Asia, Western Australia, and Northwest China. The ecowater conveyance project can effectively curb a series of ecological and environmental problems, such as desertification, biodiversity loss, and imbalance between supply and demand and uneven spatial distribution of water resources in the lower reaches of the basin [11,12,13]
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