| Under the rapid development of China's economy and society,the interference of human activities on rivers and lakes is increasing day by day.The construction of water conservancy projects has brought about many economic and social benefits,but also caused many problems of water ecological environment.How to understand the impact of water conservancy project construction on the ecological health of rivers and lakes,correctly handle various ecological and environmental problems caused by water conservancy projects,provide scientific and technological support for the construction of water conservancy projects to avoid the negative impacts of ecological environment.it has important th,eoretical and practical significance to realize the benefit of water conservancy projects and rivers and lakes' coordinated development of ecological environment.This paper takes the tail-area in the lower reaches of the Fu River in Ganjiang River as the research object,and it starts from the interaction of water and sand situation,water environment and water ecology.The comprehensive research on the water system and water in the tail-area in the lower reaches of the Fu River in Ganjiang River is comprehensively studied.Based on the ecological impact,an evaluation system for the impact of the project on the health status of the river system was constructed,and countermeasures for river and lake health protection were proposed.This article has the following innovative results:(1)The process of hydrological characteristics change in the tail-area in the lower reaches of the Fu River in Ganjiang River was expounded,and the change degree of hydrological characteristic parameters and the change law of water level during the dry period were quantitatively analyzed.The hydrological characteristics analysis results show that the main parameters of the runoff frequency analysis of the lower reaches of the Minjiang River,the lower reaches of the Fuhe River and the Qingfeng Mountain Stream are 0.29,0.37,0.39,and the Cs/Cv values are 2.0.The probabili,ty of encountering the Sanhe flood is 26%.The results of hydrological characteristic parameter change degree analysis show that:from 1956 to 1987,it can be used as a hydrological situation with less human influence,and the hydrological characteristic parameters of Shishang hydrological station are most significant.The change of water level in dry season indicates:the average annual water level of the tail decreased by 1.94m and 1.49m in the past ten years,and the annual average water level and the lowest water level showed a significant downward trend.In recent years,the measured large sections have obvious downward trend.(2)It clarifies the mechanism of the water conservancy and water conservation project to increase the synchronization of the runoff in the basin and reduce the synchronism of the sediment transport.According to the long series of data from the water station in the national basic network station,the effects of the project implementation on the water level,the probability of abundance and the change of sediment transport in the main rivers were analyzed.In terms of the impact of water level during the dry season,the water level uplift effect of the tail-water channel during the dry season is more obvious after the implementation of the project;the probability of encountering the abundance of the two groups at the two sites of Lijiadu and Waizhou hydrological stations shows that the project implementation will make the runoff of two sites synchronously increased and sediment transport synchronously decreased.The analysis of the contribution rate of sediment transport changes showed that during the period of 2003~2009,the annual cumulative soil erosion control area had the largest contribution to the annual sediment transport reduction.The average contribution of the accumulated water conservation forest area is the smallest.During the period of 2010~2016,the annual contribution of annual rainfall to the reduction of annual sediment transport is the largest,the annual cumulative soil erosion control area is second,and the average annual contribution rate of the cumulative trench dam area is the smallest.(3)The temporal and spatial variation characteristics and changes of water quality of rivers and lakes in the tail-area in the lower reaches of the Fu River in Ganjiang River are clarified.According to the water quality evaluation results of water quality monitoring data,the water quality of the tail river is mainly caused by type IV water,which is slightly polluted.The overall water quality of urban lakes is mainly inferior to V and is heavily polluted.On the time scale:river water quality deteriorates year by year.The trend of seasonal changes is:high water period>flat water period>dry season.The seasonal variation of lake water quality is as follows:flat water period>high water period>dry season;spatial scale:river water quality is better upstream than downstream,north branch is best,middle branch is slightly worse than north branch,and south branch is the worst.The water quality of the lake is that the water quality of Qingshan Lake in the central area is relatively the best.The Yaohu Lake in the outer suburbs is in the middle,and the Aixi Lake in the suburbs is the worst.The degree of river water pollution is significantly negatively correlated with the runoff and water level.(4)The water allocation plan based on water quality targets and river and lake water environment carrying capacity is proposed.Based on the hydrodynamic-water quality model constructed by MIKE11,the results of water environment carrying capacity of the main rivers and lakes are calculated.The results of the central branch,the southern branch,the main trunk west,the Qingshan Lake,the Aixi Lake and the Yaohu Lake are negative,and an effective river and lake is needed.Water replenishment measures;calculation results of river water environment carrying capacity compensation water quantity based on water function water quality target:It shows that the water replenishment range,replenishment flow,replenishment water source and water replenishment mode are determined,and the annual water environment carrying capacity compensation total water demand is about 405 million m3.Determining the implementation of the water system connection project can effectively improve the water system connectivity conditions in the tail-area in the lower reaches and significantly improve the water quality of the rivers and lakes in Nanchang.(5)The influence of the comprehensive improvement of the water system in the tail-area in the lower reaches of the Fu River in Ganjiang River on the groundwater environment in the area was identified.Through theoretical analysis and laboratory tests,the influence of river channel leakage on the water solute transport in the riverbed soil and groundwater was simulated by Hydrus-2D.The simulation results of non-adsorbed solute represented by TN showed that the riverbed stratification The TN content in the soil increased with the increase of the simulation time,and finally reached the same content as that in the overlying water.It is transported to the groundwater through the soil capillary to affect the groundwater quality.Adsorbent solutes such as TP are mainly accumulated in the surface of the riverbed soil within 1 m.The longer the simulation time,the larger the cumulative amount.The environmental carrying capacity of TP in the lm range from the surface of the river channel is 280mg/m3,and the carrying limit of groundwater to TN is 20mg/L.(6)Constructed a comprehensive water system improvement project in the tail-area in the lower reaches of the Fu River in Ganjiang River to implement the river and lake health assessment system,and put forward countermeasures for river and lake health protection.The four indicators of river hydrology and water resources,water environment,water ecology and water function are selected as the target level first-level indicators,and the AHP-FCE evaluation model is constructed.The results show that the weight of the first-level indicators is:river hydrology and water resources>water environment>ecology benefits>water function.Project implementation has the greatest impact on regional river hydrology and water resources.Evaluate the comprehensive comprehensive improvement project of the water system to control the comprehensive health status of the river section 4.0206,and the health status is "healthy";systematically analyze the response of the river terrestrial ecology,aquatic ecology and environmental impact sensitive area to the comprehensive remediation project,indicating that the project implementation has a favorable impact overall.Mainly,we propose environmental protection measures for rivers based on river and lake health. |
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