Effect Of Hydraulic Project On Regional Water Environment

There is a long history with water resources exploitation and utilization in Weihe basin. In particularly,all kinds of hydraulic projects are constructed at Guanzhong area in Shaanxi province.For example,drawing water,reservoir,and drawing ground hydraulic projects are constructed on the 5.5km~2 area.Therefore,Guanzhong area is of the magnitude,large scale and remarkabel impacting area due to constructed hydraulic projects.On the one hand, hydraulic projects promote the economic development.On the other hand,excess exploitation and utilization with water resources bring a lot of water environment problems and these problems can not be ignored.This paper studied on the relationship between hydraulic projects and water environment,and analysed the water environment problems owing to the construction of hydraulic projects.The results of research are as follows:(1) With investigation and data collection,water quantity,water quality and water environment capacity are analysed after the construction of Fengjiashan Reservior.There is significant change of water quantity by adjusting reservior.The reservior discharges water in flood season and stores water in other season.The discharge water quantity is 32 million m~3 after 1992.Because the discharge water quantity reduces,it is less than minimum stream ecological flow.By the survey prove,fish and other aquatic biology habitat environment are threatened as decreasing water quantity in the lower stream.(2) The water quality is gradeâ…¡at upper Fengjiashan Reservior in Qianyang county. However,the water quality is gradeâ… in Fenjiashan Reservior.Because of function of acceptance,purify and dilution with reservior water,the water quality is improved.In 2006 (current year),the Chemical Oxygen Demand(COD) and total phosphor(TP) water environment capacity is very great,but the water environment capacity in lower stream is influenced while the water quantity decreases as result of adjusting reservior.(3) Runoff trend is analysed by the R/S method,and water quality trend is analysed by Mann-Kendall method.Statistic results show that the trend of runoff decreases but water quality raises significantly.(4) Because of hydraulic projects impact,the annual average runoff had been reduced 2.057 billion m~3 from 1970 to 1996 accounting for 31.6%in the range lower Weihe River, compared to the runoff from 1956 to 1969.There is clear effect by hydraulic projects.(5) Water quality pollution index indicates that the level of water quality is seriously polluted in Weihe River.Take contamination of COD as an example,the result of flow adjusting contamination shows there is a negative correlation between concentration and flow.When the runoff is decreased due to the effect of hydraulic projects,the contamination of COD increases from 8.08mg/L to 20.76mg/L.Pollution contamination will enhance with the reducing runoff.Hence,hydraulic projects obviously affect the water quality in Weihe River.The hydraulic projects markedly lead the water quantity to decline and the water quality to deterioration in Weihe River at Guanzhong area.There are a series of disadvantage effects by the effect of hydraulic projects,such as reducing runoff,declining groundwater,and threatening aquatic biology habitat.The water environment problem will be serious,because of constructing hydraulic projects and increasing utilization of water resources at Guanzhong area.Runoff will be cutting off in future.Therefore,hydraulic project planning layout and construction must be highly paid attention.