| The annual averange precipitation of West Liao River basin is about375mm. The averange precipitation of West Liao River Mountain area is about375mm, where pricipitaion will produce runoff and rivers are well developed. The averange precipitation of West Liao River Plain is about368mm, where most part of the pricipitation infiltrates into soil and precipitation, infiltration and evaporation are main part of water cycle. Shallow groundwater resources accounts for77%of water resources of West Liao River basin, and it supplies about70%water for users. Because of the impact of climate changes and human activities, outflow of mountain areas runoff has reduced, and the intensity of groundwater exploitation has increased since1999. A series of eco-environment problems have appeared, including outflow reducing, groundwater table decrease and ecological vegetation degradation, which have affected the security of water supply and ecosystem of West Liao River basin. This dissertation aims at studying the water cycle regulation of West Liao Rive Basin and Plain, analysising the relationahip between water cycle system and ecosystem, and confirming ecological groundwater level to maintain ecosystem stability. Studies on water cycle regulation and relationship between water cycle system and ecosystem can not only provide technical support for decision-making about water resources sustainable exploitation and ecosystem stability maintainance, but also provide references to quantitative studies on water cycle regulaiton and relationship between water cycle system and ecosystem.Studies at home and abroad on distributed hydrological models and ecological groundwater level were reviewed in the dissertation. A distributed simulation model for water cycle of West Liao Rive Basin is constructed based on MODCYCLE model. Water cycle regulations of West Liao River Basin and Plain were analysised on the basis of simulation results in the dry series and the wet series. Relationships of "grassland yield-phreatic evaporation-groundwater depth" and "precipitation infiltration recharge-groundwater depth" were quantified, and ecological groundwater levels for ecosystem stability maintainance and groundwater protection were listed based on the statistical relations. Advices about groundwater exploitation were given based on the simulation results and ecological groundwater levels.Main results are:1. The regulation of water cycle and transformation in West Liao River Basin has been analysised based on simulation results in the dry series and the wet series. Results of water balance and groundwater recharge/discharge were quantified, and the relationships of recharge/discharge items and precipitation were studied. Changes of water cycle regulation were quantified by comparing the results of simulation in the dry series and the wet series.2. Water cycle regulation of West Liao River Plain was a type of the dualistic water cycle structure. Water cycle regulations in the dry series and the wet series were analysised, including:①water balance relationship for analysising and comparing the results of simulation in the dry series and the wet series;②evaporation structure of West Liao River Plain;③the relationship between precipitation and surface flow for analysising the mechanism and characteristics of water cycle system;④values and spacial distribution of groundwater recharge and discharge in West Liao Rive Plain.3. Ecoligical groundwater level was determained as control inditor of ecological stability. Given that the grass is a typical vegetation in West Liao Rive Plain, contributions to grassland evapotranspiration of precipitation and phreatic evaporation were analysised. Relationships of "grassland yield-phreatic evaporation-groundwater depth" and "precipitation infiltration recharge-groundwater depth" were quantified. Ecological groundwater levels aimed at maintaining ecological steability and groundwater protecting were given. Advices on groungwater exploitation for counties within West Liao River Basin were offered. |
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