Streamflow Alterations, Attributions, and Implications in Extended East Rapti Watershed, Central-Southern Nepal

Abstract

Streamflow alteration and subsequent change in long-term average, seasonality, and extremes (e.g., floods and droughts) may affect water security, which is a major concern in many watersheds across the globe. Both climatic and anthropogenic activities may contribute to such changes. Therefore, this study assesses: (i) Streamflow and precipitation trends to identify streamflow alterations in the Extended East Rapti (EER) watershed in central-southern Nepal; (ii) relationship of the alterations to climatic and anthropogenic sources; and (iii) implications of streamflow changes to the socio-environmental system. The trends in streamflow were analyzed for pre-and post-1990 periods considering the abrupt shift in temperature trend in 1990. Results showed a general decreasing trends in discharge post-1990 in the EER watershed. Human activities have significantly contributed in altering streamflow in the EER. Human-induced streamflow alterations have affected the water availability, food security, river health, aquatic biodiversity, and groundwater abstraction in the EER watershed.

Climate-Streamflow Relationship and Consequences of Its Instability in Large Rivers of Pakistan: An Elasticity Perspective

“…Climate change studies allude that variability in hydrological systems will affect important sectors, including hydropower generation, water supplies of households, and irrigation, as well as industrial demands [4][5][6]. Streamflow alteration and subsequent change in long-term averages, seasonality, and extremes (e.g., floods and droughts) may affect water security, which is a major concern in many watersheds across the globe [7]. Similarly, a lot of studies confirm that South Asia is suffering from climate change which will cause severe threats to natural environments and water resources of South Asia [7][8][9][10][11].…”

“…Streamflow alteration and subsequent change in long-term averages, seasonality, and extremes (e.g., floods and droughts) may affect water security, which is a major concern in many watersheds across the globe [7]. Similarly, a lot of studies confirm that South Asia is suffering from climate change which will cause severe threats to natural environments and water resources of South Asia [7][8][9][10][11]. The Indus basin, which starts in the Hindukush-Karakorum-Himalayan (HKH) territory, is highly prone to aggressive climate events and is reported to suffer from huge losses in terms of infrastructure, economics, and human lives [12].…”

“…High uncertainty and vulnerability of water resources in the context of climate change have become a popular research area and are considered as a burning issue. Many hydrological studies are available that assessed streamflow sensitivity in response to climate variables, particularly precipitation and evapotranspiration [7,[20][21][22][23][24]. A large share of these studies utilized suitable hydrological models by calibrating input parameters against historical streamflow data to foresee the resulting changes in water assets and the future streamflow of the region [25][26][27][28][29].…”

“…The choice of the modelling technique is relatively more reliable in giving estimates of streamflow sensitivity subject to proper calibration of a suitable model [35]. Hydrologic modelling requires accurate precipitation data at a high spatial resolution, which is often limited in many regions of the globe [7,36]. Moreover, the main problem with the modelling approach is the presence of outliers and the requirement for a continuous and comprehensive historical record of different climatic and non-climatic parameters [37].…”