Research On Ecological Water Requirement Of Wetlands In Middle And Lower Reaches Of Naoli River

Sanjiang Plain is the largest concentrated area of freshwater marsh wetland in China,which is typical and representative in the world.In recent years,due to the dual effects of natural factors and human factors,the wetland area of Sanjiang Plain is gradually shrinking,and the structure and function of wetland ecosystems were destroyed,and then the rare species were affected badly.In this paper,four nature reserves,which are well preserved in the middle and lower reaches of Naoli River,in the hinterland of Sanjiang Plain,were selected as the object of study and the ecological water demand of wetland was studied.Firstly,their degradation characteristics and causes were explored through the field investigation and data analysis.The wetland ecological restoration target is determined on several aspects and the ecological water demand of wetland was caculated by combining ecology and remote sensing technology.Finally,according to water balance,the ecological replenishment process of wetland under different scenarios was analyzed combing with wetland water supply.And from the ecological point of view,the wetland ecological replenishment effect was evaluated.The above research was to provide scientific basis for the protection and restoration of wetlands of Sanjiang plain.Research results of this paper are as follows:(1)The degradation characteristics and causes of wetland were analyzed through the field survey and data collection.The characteristics of wetland degradation are wetland groundwater level decline,wetland area shrinking and wetland biodiversity weakening.Wetland degradation is affected by natural conditions,including the temperature rise,the decrease of precipitation,the evaporation process is greater than the precipitation process,but more is affected by human activities,the most important of which is the large-scale farmland development and continuously small-scale reclamation.(2)According to the main ecological problems of wetland and the protection object,the ecological restoration target of wetland was determined synthetically.The minimum ecological restoration target is to ensure that the wetland ecosystem in the core area achieves the best condition.The suitable ecological restoration target is to restore the structure and function of the wetland ecosystem to the ideal level.The results showed that the wetland ecological restoration target was better and reasonable in the late 1990 s,and the total area of the minimum and suitable ecological restoration targets in the four nature reserves was 6.04 × 104hm2 and 16.90 × 104hm2,respectively.(3)Wetland ecological water demand can be divided into consumption of water demand and non-consumption of water demand according to wetland ecosystem water demand characteristics and the minimum and suitable ecological water demand were calculated and calculated The consumable water demand includes the water requirement for water evaporation,wetland vegetation and wetland soil.And non-consumable water demand includs biological habitat water demand.Wetland minimum and suitable ecological water demand were 6.34×108 m3 and 16.76×108 m3.(4)Based on the water balance,the ecological replenishment scenarios of wetland under different water supply were analyzed,and the ecological replenishment effect of wetland was evaluated from the ecological point of view.For the minimum wetland ecological water replenishment process,in the high-flow year and normal year,there is no need for ecological replenishment of wetlands.However,in the dry year,it is necessary to supply wetlands in August,September and October.For the suitable wetland ecological water replenishment process,regardless of water situation,it is necessary to carry out ecological replenishment of the wetland.The wetland area can reach 15.9 × 104 hm2 and the average water depth is 0.25 m after returning farmland to wetting and ecological replenishment.The vegetation types of wetland ecosystem were diverse and its tructure is stable,which can meet the needs of a certain number of different habitat birds.