The Hydrological Characteristics And The Evaluation Of Annual Runoff Of The Ephemeral Streams Around The Yanqi Basin

The Yanqi Basin is located in the northeast of Mongolian Autonomous Prefecture of Bayingolin,Xinjiang Autonomous Region.It is an inland intermountain basin at the southern foothill of Mt.Tianshan.The ephemeral streams around the Yanqi Basin finally flow into the basin and the Bosten Lake.The 80% inflow of Bosten Lake comes from the Kaidu River,the other comes from the Huangshuigou River,Qingshuihe River and Quhuigou River etc.The Yanqi Basin is the very important water source for the local area and the Tarim River.For a long time,the annual runoff of the ephemeral streams into the Yanqi Basin has been ignored when computing the water balance and the hydrologic budgets.However the water resources of the ephemeral streams have great significance for the water resources estimate and the local water balances.Meanwhile the water resource of the ephemeral streams plays a very important role for irrigating farmland,industry and people's life.Hence evaluating quantitatively the water resources of the ephemeral streams has significant meaning for the sustainable use of water resources in this region.Therefore,this article evaluates the annual runoff of the ephemeral streams around the Yanqi Basin.Basing on the physical condition of the region and the available data of hydrology and meteorology,this paper uses the following methods to evaluate the annual runoff.With the ArcGIS hydrological analysis,combining the Aster-GDEM data with the hydrologic station data and the meteorological station data,firstly the paper extracts and analyzes the hydrologic characteristics of the rivers and its streams surrounding Yanqi basin,and then extracting the watershed,river network,river profile,the zones area at different altitudes,the channel?s density and river?s profile average gradient.And using the areas at different altitudes as well as the lapse rate of the rainfall,the annual total precipitation and the runoff coefficients of these basins has beenevaluated,finally calculating the annual runoff volume of overall the area.The results show that:(1)The network density of the whole area is 0.163km/km2.The whole area is divided into 10 sub-catchments,among them,the river ? s density of the Huangshuigou River,Qingshuihe River and Quhuigou River are 0.146km/km2,0.177km/km2 and 0.175km/km2.The network density of the southeast slope is the largest of 0.216km/km2 and the east slope is the smallest of 0.063km/km2.(2)The length of the Huangshuigou River,Qingshuihe River,Quhuigou River and Chahantonggu River are 108.43 km,61.67 km,42.54 km and 58.95 km.,the stream average gradient of this four river are 18.5‰,32.9‰,46.1‰ and 32.1‰.(3)This paper computes the annual total precipitation of each sub-catchment from1956 to 2007.The annual average total precipitation of the Huangshuigou River is the largest of 8.08×108m3,Qingshuihe River is 2.56×108m3 and Chahantonggu River is2.29×108m3.The annual average total precipitation of the north slope is the smallest of0.88×108m3.(4)This article computes the runoff coefficient of the Huangshuigou River and Qingshuihe River from 1956 to 2007,the average runoff coefficient of them are 0.337 and 0.407.The runoff coefficient of the Chahantonggu River is 0.23 calculated by the data of 1957.(5)This article calculates the annual runoff volume of each sub-catchment from 1956 to 2007 and the average annual runoff volume of them.The annual average runoff volume of the Huangshuigou River is 2.72×108m3 larger than the data of hydrologic station of 2.51×108m3.The annual average runoff volume of the Qingshuihe River is1.04 × 108m3 larger than the data of hydrologic station of 1.03 × 108m3.The annual average runoff volume of the north slope is the smallest of 0.2×108m3.Adding all the annual average runoff volume of each sub-catchment together,we get the annual average runoff volume of the whole area of 7.87×108m3.The annual average runoff volume of the Kaidu River is 34.87×108m3 and the total annual average runoff volume flowing into the Bosten Lake is 42.74×108m3.Hence,the annual average runoff volume of the Kaidu River accounts for over 80% of the Bosten Lake.