Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin, Nepal

The Himalayas, especially the Everest region, are highly sensitive to climate change. Although there are research works on this region related to cryospheric work, the ecological understandings of the alpine zone and climate impacts are limited. This study aimed to assess the changes in surface water including glacier lake and streamflow and the spatial and temporal changes in alpine vegetation and examine their relationships with climatic factors (temperature and precipitation) during 1995–2019 in the Everest region and the Dudh Koshi river basin. In this study, Landsat time-series data, European Commission’s Joint Research Center (JRC) surface water data, ECMWF Reanalysis 5th Generation (ERA5) reanalysis temperature data, and meteorological station data were used. It was found that the glacial lake area and volume are expanding at the rates of 0.0676 and 0.0198 km3/year, respectively; the average annual streamflow is decreasing at the rate of 2.73 m3/s/year. Similarly, the alpine vegetation greening as indicated by normalized difference vegetation index (NDVI) is increasing at the rate of 0.00352 units/year. On the other hand, the annual mean temperature shows an increasing trend of 0.0329 °C/year, and the annual precipitation also shows a significant negative monotonic trend. It was also found that annual NDVI is significantly correlated with annual temperature. Likewise, the glacial lake area expansion is strongly correlated with annual minimum temperature and annual precipitation. Overall, we found a significant alteration in the alpine ecosystem of the Everest region that could impact on the water–energy–food nexus of the Dudh Koshi river basin.

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Spatiotemporal analysis of water resources system vulnerability in the Lancang River Basin, China

Journal of Hydrology ◽

10.1016/j.jhydrol.2021.126614 ◽

2021 ◽

pp. 126614

Author(s):

Zihan Gui ◽

Xiaohong Chen ◽

Yanhu He

Keyword(s):

Water Resources ◽

River Basin ◽

Spatiotemporal Analysis ◽

Water Resources System ◽

Lancang River ◽

System Vulnerability ◽

The Lancang River Basin

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Vegetation Changes and Their Response to Global Change Based on NDVI in the Koshi River Basin of Central Himalayas Since 2000

Sustainability ◽

10.3390/su12166644 ◽

2020 ◽

Vol 12 (16) ◽

pp. 6644

Author(s):

Xue Wu ◽

Xiaomin Sun ◽

Zhaofeng Wang ◽

Yili Zhang ◽

Qionghuan Liu ◽

...

Keyword(s):

Climate Change ◽

Land Cover ◽

River Basin ◽

Human Activities ◽

Vegetation Change ◽

Precipitation Trend ◽

Central Himalayas ◽

Annual Minimum Temperature ◽

Vegetation Activity ◽

Koshi River Basin

Vegetation forms a main component of the terrestrial biosphere owing to its crucial role in land cover and climate change, which has been of wide concern for experts and scholars. In this study, we used MODIS (moderate-resolution imaging spectroradiometer) NDVI (Normalized Difference Vegetation Index) data, land cover data, meteorological data, and DEM (Digital Elevation Model) data to do vegetation change and its relationship with climate change. First, we investigated the spatio-temporal patterns and variations of vegetation activity in the Koshi River Basin (KRB) in the central Himalayas from 2000 to 2018. Then, we combined NDVI change with climate factors using the linear method to examine their relationship, after that we used the literature review method to explore the influence of human activities to vegetation change. At the regional scale, the NDVIGS (Growth season NDVI) significantly increased in the KRB in 2000–2018, with significant greening over croplands in KRB in India. Further, the croplands and forest in the KRB in Nepal were mainly influenced by human interference. For example, improvements in agricultural fertilization and irrigation facilities as well as the success of the community forestry program in the KRB in Nepal increased the NDVIGS of the local forest. Climate also had a certain impact on the increase in NDVIGS. A significant negative correlation was observed between NDVIGS trend and the annual minimum temperature trend (TMN) in the KRB in India, but an insignificant positive correlation was noted between it and the total annual precipitation trend (PRE). NDVIGS significantly decreased over a small area, mainly around Kathmandu, due to urbanization. Increases in NDVIGS in the KRB have thus been mainly affected by human activities, and climate change has helped increase it to a certain extent.

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How size and trigger matter: analyzing rainfall- and earthquake-triggered landslide inventories and their causal relation in the Koshi River basin, Central Himalaya

10.5194/nhess-2018-109 ◽

2018 ◽

Cited By ~ 2

Author(s):

Jianqiang Zhang ◽

Cees J. van Westen ◽

Hakan Tanyas ◽

Olga Mavrouli ◽

Yonggang Ge ◽

...

Keyword(s):

River Basin ◽

Causal Relation ◽

Anthropogenic Activities ◽

Slope Angle ◽

Central Himalaya ◽

Triggering Mechanism ◽

Susceptibility Maps ◽

Triggering Mechanisms ◽

Koshi River Basin ◽

Frequency Area

Abstract. Inventories of landslides caused by different triggering mechanisms, such as earthquakes, extreme rainfall events or anthropogenic activities, may show different characteristics in terms of distribution, causal factors and frequency-area relationships. This research aims to study such differences in landslide inventories, and the effect they have on landslide susceptibility assessment. Koshi River basin in central Himalaya was taken as study area. Detailed landslide inventories were generated based on visual interpretation of remote sensing images and field investigation for different time periods and triggering mechanisms. Maps and images from the period 1992 to 2015 were used to map 5,858 rainfall-triggered landslides and after the 2015 April 25 Gorkha earthquake, an additional 1138 co-seismic landslides were mapped. A set of topographic, geological and land cover factors were employed to analyze their correlation with different types and sizes of landslides. The results show that the frequency – area distributions of rainfall and earthquake–triggered landslides varied considerably, with the former one having a larger frequency of small landslides. Also topographic factors varied considerably for the two triggering events, with both elevation and slope angle showing significantly different patterns for earthquake-triggered and rainfall-triggered landslides. Landslides were classified into two size groups, in combination with the main triggering mechanism (rainfall- or earthquake-triggered). Susceptibility maps for different combinations of landslide size and triggering mechanism were generated using logistic regression analysis. The different triggers and sizes of landslide data were used to validate the models. The results showed that susceptible areas for small and large size rainfall- and earthquake-triggered landslides differed substantially, while susceptibility maps for different size of earthquake-triggered landslides were similar.

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