Snow cover, snowmelt and runoff in the Himalayan River basins
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Abstract:
Not withstanding the seasonal vagaries of both rainfall amount and snowcover extent, the Himalayan rivers retain their basic perennial character. However, it is the component of snowmelt yield that accounts for some 60 to 70 percent of the total annual flow volumes from Hamilayan watersheds. On this large hydropotential predominantly depends the temporal performance of hydropower generation and major irrigation projects. The large scale effects of Himalayan snowcover on the hydrologic responses of a few selected catchments in western Himalayas was studied. The antecedent effects of snowcover area on long and short term meltwater yields can best be analyzed by developing appropriate hydrologic models forecasting the pattern of snowmelt as a function of variations in snowcover area. It is hoped that these models would be of practical value in the management of water resources. The predictability of meltwater for the entire snowmelt season was studied, as was the concurrent flow variation in adjacent watersheds, and their hydrologic significance. And the applicability of the Snowmelt-Runoff Model for real time forecast of daily discharges during the major part of the snowmelt season is examined.Keywords:
Snowmelt
Meltwater
Snowpack
Water year
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Based on the basic principle of the HBV conceptual hydrological model, a hydrological model of the mountainous watersheds in the arid inland area of northwest China was developed by the authors. This model reflects the characteristics of the runoff generation in the mountainous watersheds of west China. The model simulates the runoff formation and transformation processes of the mountainous watersheds by dividing the watersheds into two basic altitude zones, the high mountain ice and snow zone and the mountain vegetation zone. Taking the monthly air temperature and precipitation of the standard meteorological stations as the foremost inputs to the model, the monthly runoff from the mountainous watersheds is then simulated. The model is applied to simulate the water balance of a mountainous watershed of the Heihe River basin at the north flank of the Qilian mountains, and the annual runoff and its monthly distribution is then forecasted. The results indicate that, from the dry years to the wet years, all of the precipitation, evaporation, runoff and runoff coefficient increase, but the alimentation proportion of glacial meltwater and snow meltwater to the total runoff decrease. Therefore, the ice and snow meltwater plays a regulation function for the runoff. In the mountainous watershed of the Heihe River, the runoff coefficient is much larger than that of the whole arid area, but it is still less than the average value over the whole country. The model of runoff simulation and forecast for the inland mountainous watersheds applied in the present study shows rather good fitness in the forecast of the annual runoff and its monthly distribution. Therefore, the model can be used for the runoff forecast of the mountainous watersheds both of the Heihe River and other inland rivers of the arid area of northwest China. And this will serve the rational allocation, utilization and exploitation of water resources in the middle and down courses of the inland river basins.
Meltwater
Water balance
Snowmelt
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Hydrological modelling
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Snowpack
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Variation (astronomy)
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我が国の日本海側の地域では,Rain-on-Snow (RoS)に伴う融雪出水が冬季に極端化すると予測されている.本研究の目的は,RoS起因の融雪出水に対する気候変動の影響を流域スケールで評価することである.本研究は庄川流域を対象として,積雪・融雪過程を考慮した水文モデルに気候予測データベース(d4PDF)の気象データを標高に応じて適切に入力した.温暖化に伴い,平均的な融雪出水量は減少するものの,これまでよりも大きい融雪出水ピーク流量が出現することが示唆された.RoS起因のピーク流量も温暖化に伴い極端化する結果となった.RoS起因の極端なピーク流量は現在気候の12~3月においてほとんど出現しなかったが,将来気候において頻出することが示唆された.
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Index method for forecasting Apr through Sept runoff for Columbia River at Dalles, Ore, is presented, based on relationship between winter runoff in coastal drainage areas and spring snowmelt runoff of Columbia River; reliability of forecasts is comparable with those based on precipitation and snowcourse data.
Snowmelt
Water year
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Snowmelt
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Abstract. Glaciers are one of the most important water supplies of glacierized catchments in Central Asia. Therefore, the effects of climate change on glaciers, snow cover and permafrost will have increasingly significant consequences for runoff. Hydrological modeling has become an indispensable research approach to water resources management in large glacierized river basins, but there is a lack of focus in the modeling of glacial discharge. This paper reviews the status of hydrological modeling in glacierized catchments of Central Asia, discussing the limitations of the available models and extrapolating these to future challenges and directions. After reviewing recent efforts, we conclude that the main sources of uncertainty in assessing the regional hydrological impacts of climate change are the unreliable and incomplete datasets and the lack of understanding of the hydrological regimes of glacierized catchments of Central Asia. Runoff trends indicate a complex response of catchments to changes in climate. For future variation of water resources, it is essential to quantify the responses of hydrologic processes to both climate change and shrinking glaciers in glacierized catchments, and scientific focus should be on reducing these uncertainties.
Water cycle
Central Asia
Meltwater
Hydrological modelling
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