Study On Ecological Water Requirements In Zhalong Wetland

Zhalong Wetland is the largest national natural protection area Characterized by crane,waterfowl's habitat and typical wetland ecological type. The geographical coordinate iseast longitude 1235°1.5′～124°37.5,′north latitude 464°8～′47°31.5′ with a total area of21×104hm2, ii which care area ,where is an important habitat for waterfowls, is700km~2;Buffer area 670km~2;experiment area is 730km~2. Zhalong Wetlandkeeps original landscape and is rich in biodiversity. There are 266 kinds ofbirds, 83 kinds of beast, fish, amphibious animals and creeper, vascular bundleplants. And many waterfowls take the place as an ideal breeding place;manybirds take the place as a stopping place. The crane number which Grus remainsdominant is very large and crane population accounts for 17.3% of world total.The supper geographical location and unique natural and ecologicalenvironment make the wetland become a paradise for waterfowls and birdsimmigrating from north to south. The wetland plays a very important role inregulating regional climate, balancing precipitation, retaining flood, purifyingwater body and reducing pollution. Therefore protecting the wetland has greatsignificance in the world.With the population increase and economic development, especiallycontinuous dry year in recent years, the wetland area and crane numberdecrease greatly, biodiversity is damaged and the wetland is facing degrading,even facing the threat of disappearing. The ecosystem of the wetland need tobe saved urgently, and environmental and ecological water requirementbecome hot issue. Water resources are a main protection target for wetlandprotection. It has an important significance to carry out environmental andecological water requirement study, make wetland enter sound circulation ofecological, economic and social benefits for Zhalong Wetland.The paper takes environmental and ecological water requirement inZhalong Wetland as a research example, analyzes the formation, historicvariation, basic function, ecological resources and existing environmentalissues beginning with existing condition investigation and remote sensingpicture explanation, then puts forward calculation method for environmentaland ecological water requirement in Zhalong Wetland.The study for environmental and ecological water requirement startedabroad and mainly focused on rivers. It is just a beginning period forsymmetrically studying environmental and ecological water requirement inChina. There are no consistent definition for the conception, the connotationand the extension of environmental and ecological water requirement. Thecalculation method for environmental and ecological water requirement is notcomplete and perfect, and remains in the period of qualitative analysis andmacro-quantitative analysis. At the present there are a little research ofenvironmental and ecological water requirement for wetland comparatively.In the broad sense environmental and ecological water requirement is thewater that maintains wetland existence and development, and wetlanddelivers its ecological function;in the narrow sense environmental andecological water requirement is the water that replenishes consumed water bythe wetland ecosystem every year. The environmental and ecological waterrequirement in the paper refers to the inflow in a dry year that can make thewetland restore natural conditions, which maintain normal existence for thewetland ecosystem and a definite area at the core area in the dry year.The hydrological elements of Zhalong Wetland are a complicated system,including inflow, runoff, outflow, evaporation and connection withgroundwater, namely a complicated circulation. The paper defines theminimum environmental and ecological water requirement as the inflow in adry year which can restore the wetland to natural condition. Based on abovedefinition and the analysis data of hydrological elements in many years,environmental and ecological water requirement for the wetland is determinedby water balance method.In the calculation, weight average loss depth of the wetland is calculatedaccording to the proportion of reed area and water surface;the capacity curvefor the wetland is obtained in light of three-dimensional map produced fromdigitalized 1/10000 relief map of Zhalong Wetland;the water surface areafor each region is measured by using explained satellite map in differentperiods and the storage corresponding water surface area can be checked fromthe capacity curve. Adding up the storage in different regions, wetland storageis obtained for the corresponding period and the relation of wetland watersurface and storage is established. In accordance of natural inflow series from1956~ 1956 in Wushuang Catchments, taking hydraulic year (year) ascalculating period and considering the water surface area in the end of a yearas water replenishing controlling condition, balance calculation for thewetland is carried out. By means of explained satellite maps, suitable andminimum water surface area is decided for maintaining wetland in normal, dryand special dry years. On the basis of deciding the calculation parameters andthe wetland inflow of Zhalong Wetland after supply and demand balance isconducted for Wushuang Catchments, considering the fact that water supplyfrom Nenjiang River Diversion Project for the wetland will be increased afterconveyance system of Ni'erji Reservoir is completed, water balance iscalculated for Zhalong Wetland.In terms of water balance, environmental and ecological waterrequirement for Zhalong Wetland is predicted and analyzed. The balanceresults show that suitable annual average environmental and ecological waterrequirement for Zhalong Wetland is 4.56×108m3;minimum environmentaland ecological water requirement of 75% guarantee probability is2.60×108m3 and minimum environmental and ecological water requirement of95% guarantee probability is 1.53×108m3.The paper calculates the environmental and ecological water requirementfor Zhalong Wetland by water balance method. The method takes fully socialand economic development, human being and nature and the relation ofhuman and wetland into considerations.