Assessing the characteristics of extreme floods in Nepal

This study examines the characteristics (magnitudes, trends, and frequency of occurrences) of extreme floods in Nepal, a country that is at significant risk from floods. Daily discharge data from 1980 to 2015 of three gauging stations (Chisapani of Karnali Basin, Devghat of Narayani Basin, and Chatara of Koshi Basin) were used to assess the largest 1 % of flows, the annual top five high flows, and floods of different return periods (2-, 5-, 10-, 20-, and 100-year). In addition, temporal trend analysis of the flood peaks was carried out using the Mann–Kendall test and Sen's slope estimates. Results show that the magnitudes of the largest 1 % flows range from 6310 to 17 900, from 6967 to 12 100, and from 6080 to 9610 m3 s−1 at Chisapani, Devghat, and Chatara, respectively. The monsoon, especially from mid-June to early September, consistently witnesses over 90 % of 1 % extreme flows, with August registering more than 51 % of these occurrences. July and August combine for 81 % of the top five flow events, predominantly in August. Despite insignificant flow changes at a 95 % confidence level, extreme floods (2-, 5-, 10-, 20-, and 100-year return periods) are concentrated heavily in July and August, with August's second fortnight recording the most flood events. This assessment emphasizes July and August as critical months for extreme floods, aiding Nepalese authorities in planning dynamic resource allocation, disaster response, and effective flood management.</p

Nepal Himalaya Offers Considerable Potential for Pumped Storage Hydropower

There is a pressing need for a transition from fossil-fuel to renewable energy to meet the increasing energy demands and reduce greenhouse gas emissions. The Nepal Himalaya possesses substantial renewable energy potential that can be harnessed through hydropower projects due to its peculiar topographic characteristics and abundant water resources. However, the current exploitation rate is low owing to the predominance of run-of-river hydropower systems to support the nation's power system. The utility-scale storage facility is crucial in the load scenario of an integrated Nepalese power system to manage diurnal variation, peak demand, and penetration of intermittent energy sources. In this study, we first identify the potential of pumped storage hydropower across the country under multiple configurations by pairing lakes, hydropower projects, rivers, and available flat terrains. We then identify technically feasible pairs from those of potential locations. Infrastructural, environmental, operational, and other technical constraints govern the choice of feasible locations. We find the flat land-to-river configuration most promising over other configurations for Nepal. Our results provide insight into the potential of pumped storage hydropower and are of practical importance in planning sustainable power systems in the Himalayas

Past and future variability in the hydrological regime of the Koshi basin, Nepal

Planning adaptation strategies in response to climate change (CC) can be a daunting task, especially in regions such as the Koshi Basin in the Himalayas; where CC impacts are still uncertain. This paper recommends targeting adaptation strategies by focusing on changes in variability between the past and future climates at smaller scales. The Soil and Water Assessment Tool (SWAT) and the Indicators of Hydrologic Alteration (IHA) are used for analysis. Results show: (i) higher maximum precipitation during monsoon and post-monsoon, and lower maximum precipitation during winter; (ii) increase in precipitation and flows in the trans mountain region during all seasons, except for flows during monsoon; (iii) increase in post-monsoon precipitation and routed flow volumes; (iv) decrease in precipitation during winter and routed flow volumes in all the regions, except the trans mountain region; and (v) increase in frequency of high peak flows and decrease in baseflows

Assay of renewable energy transition: A systematic literature review

Issues of environmental degradation, finite quantity and uneven spatial distribution of fuels in nature, and growing demand accentuated by volatility of oil prices have led to the global clean renewable energy transition (RET). With an objective of examining the current knowledge-stock on RET, we reviewed 248 journal publications pooled from three databases (ScienceDirect, Web of Science and Scopus) using a Systematic Literature Review method. This study does not focus on the specifications of a particular energy technology or regress relations among a limited set of variables. Rather, the key contribution is the critical assessment of the factors that encourage and those that hinder the transition process to provide a wider perspective through seven broad lenses: technological, investment, market, environmental, government and institutional, policy and social. Research, development and implementation of technology is a direct outcome of policy investment. Developed countries are leading the RET research while the global south is far behind. Most of the studies were found to be donor-driven which faced a serious risk of being counter-welcomed in different settings of the world without compromising the objectives of the transition. A strong international collaboration among the rich and poor countries is urgently felt necessary to foster mutual benefits. Research, planning and implementation of the RET would be highly effective and sustainable through a participatory bottom-up approach promoting local technology instead of imposed expensive imported ones. The need for “demand-pull” and “technology-push” policy instruments is stringent for successful transition. We conclude that there is a unanimous agreement among all the studies on the future prospects of renewable energy in the electricity sector; however, some skepticism still exists regarding other high energy demanding areas. Our review recommends updating existing and designing new robust policy mixes to guide the modality and pace of the RET, adhering to local specificities

Application of machine learning to assess people's perception of household energy in the developing world: A case of Nepal

Research on social aspects of energy and those applying machine learning (ML) is limited compared to the ‘hard’ disciplines such as science and engineering. We aim to contribute to this niche through this multidisciplinary study integrating energy, social science and ML. Specifically, we aim: (i) to compare the applicability of different ML models in household (HH) energy; and (ii) to explain people's perception of HH energy using the most appropriate model. We carried out cross-sectional survey of 323 HHs in a developing country (Nepal) and extracted 14 predictor variables and one response variable. We tested the performance of seven ML models: K-Nearest Neighbors (KNN), Multi-Layer Perceptron (MLP), Extra Trees Classifier (ETC), Random Forest (RF), Ridge Classifier (RC), Multinomial Regression–Logit (MR-L) and Probit (MR-P) in classifying people's responses. The models were evaluated against six metrics (confusion matrix, precision, f1 score, recall, balanced accuracy and overall accuracy). In this study, ETC outperformed all other models demonstrating a balanced accuracy of 0.79, 0.95 and 0.68 respectively for the Agree, Neutral and Disagree response categories. Results showed that, compared to conventional statistical models, data driven ML models are better in classifying people's perceptions. It was seen that the majority of the surveyed people from rural (68%) and semi-urban areas (67%) tend to resist energy changes due to economic constraints and lack of awareness. Interestingly, most (73%) of the urban residents are open to changes, but still resort to fuel-stacking because of distrust in the state. These grass-root level responses have strong policy implications

Assessing the past and adapting to future floods: a hydro-social analysis

Floods are extreme events affecting millions of people worldwide and causing loss worth billions. The magnitude and frequency of floods are likely to increase with altered climate, and developing countries tend to suffer the most because of low resilience and adaptive capacity. This research aimed to analyze existing and preferred future flood adaptation strategies in a flood-prone West Rapti River (WRR) Basin of Nepal, using hydrological analysis and flood modelling, and a social survey of 240 households (HHs) and several focus group discussions (FGDs). The specific objectives were to (1) understand the rainfall-flood behaviour of the basin in a simplistic way, (2) carry out flood modelling to generate inundation maps for informing the local people, and (3) identify flood adaptation strategies based on people’s perception. Flood inundation maps are generated for four scenarios based on return periods: scenario I (2 years), scenario II (20 years), scenario III (50 years), and scenario IV (100 years). Results show that the southern parts of three rural municipalities (Duduwa, Narainapur, and Rapti Sonari) get inundated almost every year irrespective of the flood magnitude. This information was presented to local communities before administering the HH survey and FGDs so that they could make informed decisions. During the survey, the preference of people’s adaptation strategies for the four flood scenarios was explored and prioritized. Our findings suggest that peoples’ thoughts and preferences for adaptation strategies changed with exposure to flood magnitudes. For example, “bamboo mesh with sand filled bags”—simplest and least expensive adaptation strategy—was preferred for a less severe flood while a complex and expensive technique “reservoir/flood regulating structures” was preferred for a devastating flood scenario. Thus, this study has highlighted firstly, the importance of inundation maps to understand and inform the local people about floods and their impacts; and secondly, the value of information to the people enabling them to make informed decisions. The novelty of this empirical study lies in a multi-disciplinary assessment framework which integrates scientific information, stakeholder knowledge, and local people’s perceptions of flood risks and adaptation strategies for the future. Such an approach of hydro-social analysis has the potential for replication in flood-prone regions globally, with similar bio-physical and socio-economic conditions

Agriculture under changing climate conditions and adaptation options in the Koshi Basin

Using biophysical and social analysis methods, this paper evaluated agricultural practices under changing climate in the Koshi Basin and assessed adaptation options. Agricultural trend analysis showed that in the recent three to four decades, the total cultivated area had declined in all parts of the basin except in the Nepal Mountain Region. Household survey results also confirmed such decline and further revealed shifts towards non-agricultural activities. Climate trend analysis showed changes in the frequency of wet and dry days in study districts, implying an increasing chance of flood and drought events. Household surveys further revealed that, in general, people perceived a decline in agricultural water availability and an increase in drought and flood events. The direct impacts of these changes were reduced crop yield, increased fallow lands, displacement of people from settlement areas, sedimentation of cultivable land and damage to properties. Household surveys showed that despite the perceived impacts on agriculture and livelihoods, only limited adaptation options are currently practised. Adaptation efforts are constrained by several factors, including: finance; technical knowledge; lack of awareness about adaptation options; lack of collective action; unclear property rights; and ineffective role of state agencies

The projected impact of climate change on water availability and development in the Koshi Basin, Nepal

Water has been identified as a key resource for Nepal's economic growth. Although the country has 225 billion cubic meters of water available annually, less than 7% has been utilized. Climate change is a frequent topic in national development discussions in part because of its possible impact on future water availability. This study assessed the likely impact of climate change on water resources development in the Koshi River basin, Nepal, using the Soil and Water Assessment Tool to generate projections for the 2030s and 2050s. Results suggested that the impacts are likely to be scale dependent. Little impact is projected at annual, full-basin scales; but at sub-basin scale, under both the IPCC's A2 and B1 scenarios, precipitation is projected to increase in the upper transmountain subwatersheds in the 2030s and in most of the basin in the 2050s and to decrease in the lower sub-basins in the 2030s. Water yield is projected to increase in most of the basin except for the A2 scenario for the 2030s. Flow volumes are projected to increase during the monsoon and postmonsoon but decrease during the winter and premonsoon seasons. The impacts of climate change are likely to be higher during certain seasons and in some sub-basins. Thus, if infrastructure is in place that makes it possible to store and transfer water as needed, the water deficit due to any changes in rainfall or flow patterns could be managed and would not be a constraint on water resources development. The risks associated with extreme events such as floods and droughts should, however, also be considered during planning

How will hydro-energy generation of the Nepalese Himalaya vary in the future? A climate change perspective

Despite being one of the proven clean-energy technologies, hydroelectricity is losing attention in global research. Hydroelectricity is extremely important for countries possessing the required water resources, already heavily reliant on it and those lacking the financial capacity to invest in other expensive energy technologies. This study assessed the possible impact of climate change (CC) on hydro-energy generation in the Nepalese Himalaya (possessing eight peaks out of 14 over 8000 m) with a tremendous hydropower potential (∼50,000 MW). A planned 1200 MW storage type Budhigandaki Hydroelectricity Project is taken as a case. We estimated the energy generation for the baseline as well as 10 CC scenarios considering RCPs 4.5 and 8.5 at monthly, seasonal, and annual temporal scales for the mid-century. Results show that energy generation is highly dependent on the reservoir operating rule. The average annual energy generation is expected to vary within −5 to +12% of the base case in the mid-century, with significant variations across the months. We also infer that designing hydro-projects based on ensembled climate values could lead to a “rosy” but less probable and risky picture of energy generation in the future. Therefore, assessment of a wide spectrum of plausible CC scenarios are recommended. Storage type projects with provision of flexible operating rules considering finer temporal resolution and allocation to competing users (in case of multipurpose projects) supported by appropriate policies are desirable for climate resiliency. Complementing the existing energy generation mix with other technologies in areas where hydroelectricity is expected to undergo adverse impacts of CC is warranted for attaining future energy security and environmental safeguarding. Possibility of additional energy due to CC is a strong motivation for this region to focus on hydroelectricity development in the future

Impact of planned water resource development on current and future water demand of the Koshi river basin, Nepal

Water resources of the Koshi Basin (87,311km2) are largely untapped, and while proposals for their development exist, their impacts on current and future water demands are not quantified. The current study is the first to evaluate the impacts of 11 proposed development projects on hydropower generation and water storage. Results revealed that 29733GWh hydropower can be generated and 8382Million m3 (MCM) of water can be stored annually. This can satisfy unmet demands in current (660MCM) basin situation and future scenarios - i.e. population, agricultural and industrial growth – that are projected to have 920, 970 and 1003MCM unmet-demands, respectively by 2050