Effects of Water Replenishment from Yellow River on Water Quality of Hengshui Lake Wetland

Hengshui Lake Wetland is the only national wetland and bird nature reserve in the North China Plain. It plays an important role in maintaining the species diversity and ecological balance. In recent years, due to industrial and agricultural production, infrastructure and ecological environment construction and other reasons, the infiltration, runoff, evapotranspiration and other water balance elements was changed, which reduced runoff into the lake. In order to ease the tense water resources situation in the region, Hengshui Lake is replenished each year by Yellow River water. Although Diversion Yellow River Wetland has made direct water supply protection, but also affected the ecology and environment of Hengshui Lake wetlands. In order to understand how artificial water diversion can affect the ecological environment of natural lakes, this paper analyzes the effects of artificial water storage on the water quality of the lake by using the measured data of water samples in the lake. The results showed that the water level of Hengshui Lake showed an upward trend after the diversion from the Yellow River. Comprehensive pollution index showed a downward trend, but Hengshui Lake wetlands are still slightly polluted. Diversion of Yellow River diversion into the lake of the ecological health of Hengshui also caused some impact. DOI : 10.14302/issn.2637-6075.jpae-18-1937 Corresponding Author: Ma Muyuan, Institute of Wetland Research, Chinese Academy of Forestry, Beijing Key Laboratory of Wetland Services and Restoration, Beijing 100091, China. Email: xiaogu67@sina.com


Introduction
Wetland is one of the most widely distributed and productive natural ecological environment types in the world [4]. Wetland has conserved water source, purify water quality, control flood, regulating climate, control soil erosion and reduce environmental pollution.
It can also provide a wide range of products to humans and leisure places, has great economic value and social value. Healthy wetland ecosystem is an important part of ecological security and an important foundation for sustainable economic and social development.
Over the past 150 years, due to changes in the natural environment and the impact of human activities, more than 50% of the world's wetlands have been degraded or lost [1]. About 26 percent of wetlands are used for agricultural production [3] . In the UK, about 23 percent of estuarine wetlands and 40 percent of meadow wetlands are destroyed. In southern Africa, 58 percent of natural wetlands in the Mfolozi valley and 90 percent of wetlands in the Tugela basin have disappeared [6]. In southeast Asia, most wetlands have been reclaimed for residential and agricultural land. 78 percent of natural swamp wetlands in Sanjiang plain, China's largest freshwater swamp wetland, are gradually disappearing in recent 50 years. The loss and degradation of wetlands has weakened the wetland ecological service function [7].
Hydrological conditions are the characteristics of the wetland degradation factors. It is also the driving factor of other feature factors such as wetland biology and soil [5]. Therefore, it is essential to improve and restore the hydrological conditions during the restoration of wetland conservation and ecological functions.

Methods
The sampling sites were located in Wangkou Using the comprehensive pollution index analysis before and after the water transfer Hengshui Lake water quality situation: is the comprehensive pollution index; n is the number of pollutants; is the measured concentration of the i pollutants; is the evaluation standard value of the i pollutants.

Results and Discussion
The water flow into the Hengshui Lake mainly includes precipitation and the inflow of five rivers.
Hengshui Lake outflow of water in addition to evaporation and leakage, but also includes industrial  It can be seen from the figure 3 that the water quality of Hengshui Lake has been obviously improved Hengshui Lake has also hosted the marathon, but also from another aspect to the water quality of Hengshui Lake put forward higher requirements. Hengshui Lake summer water transfer is also part of this reason.
It can be seen from the figure 4, there was not much difference between the water quality before and after water diversion before 2000, and the impact of water diversion on water quality was relatively small.
After 2000, the gap between the water quality before and after water diversion is gradually revealed, and the role of water diversion is also highlighted. Especially after 2010, the water quality before water diversion Pn is about 0.5, and the water quality Pn after water diversion will be reduced to about 0.4. It shows that the pollution of Hengshui Lake has been basically stable in recent years. Appropriate water diversion can obviously reduce water pollution. At the same time, the effect of the introduction of the Yellow River water on biological species was more significant. The algae and zooplankton in the aquatic plants in the lake after the Yellow River were significantly increased. The algae increased by 56 genera, and the zooplankton increased by 81 genera [2]. The effects of rainfall and inbound flood on the biological species of Hengshui Lake were not obvious.

Conclusion
(1) Water diversion in time from the Yellow River can replenish the amount of water coming into the lake in Hengshui Lake. Frequent dry-up in the lake area has been alleviated. However, the restore ecological environment of Hengshui Lake still needs to be further studied and determined. Hengshui Lake wetland water  supply protection measures still need to be studied.
(2) The comprehensive pollution index of Hengshui Lake has a decreasing trend since the Yellow River. However, when the Yellow River water is introduced, the Rushes and other pollutants in the Yellow River basin will be introduced into Hengshui Lake with the river water. The related governance measures need further study.
(3) The amount of sand in the lake has a certain impact on the ecological health of Hengshui Lake. The Yellow River is the river with the largest amount of sediment in our country. Although sediment has been settled before the Yellow River enters Hengshui Lake, some sediment is still introduced into Hengshui Lake. This problem should also be taken seriously.