Existing climate projections and impact assessments in Nepal only consider a limited number of generic climate indices such as means. Few studies have explored climate extremes and their sectoral ...implications. This study evaluates future scenarios of extreme climate indices from the list of the Expert Team on Sector-specific Climate Indices (ET-SCI) and their sectoral implications in the Karnali Basin in western Nepal. First, future projections of 26 climate indices relevant to six climate-sensitive sectors in Karnali are made for the near (2021–2045), mid (2046–2070), and far (2071–2095) future for low- and high-emission scenarios (RCP4.5 and RCP8.5, respectively) using bias-corrected ensembles of 19 regional climate models from the COordinated Regional Downscaling EXperiment for South Asia (CORDEX-SA). Second, a qualitative analysis based on expert interviews and a literature review on the impact of the projected climate extremes on the climate-sensitive sectors is undertaken. Both the temperature and precipitation patterns are projected to deviate significantly from the historical reference already from the near future with increased occurrences of extreme events. Winter in the highlands is expected to become warmer and dryer. The hot and wet tropical summer in the lowlands will become hotter with longer warm spells and fewer cold days. Low-intensity precipitation events will decline, but the magnitude and frequency of extreme precipitation events will increase. The compounding effects of the increase in extreme temperature and precipitation events will have largely negative implications for the six climate-sensitive sectors considered here.
While the water–energy–food nexus approach is becoming increasingly important for more efficient resource utilization and economic development, limited quantitative tools are available to incorporate ...the approach in decision-making. We propose a spatially explicit framework that couples two well-established water and power system models to develop a decision support tool combining multiple nexus objectives in a linear objective function. To demonstrate our framework, we compare eight Nepalese power development scenarios based on five nexus objectives: minimization of power deficit, maintenance of water availability for irrigation to support food self-sufficiency, reduction in flood risk, maintenance of environmental flows, and maximization of power export. The deterministic multi-objective optimization model is spatially resolved to enable realistic representation of the nexus linkages and accounts for power transmission constraints using an optimal power flow approach. Basin inflows, hydropower plant specifications, reservoir characteristics, reservoir rules, irrigation water demand, environmental flow requirements, power demand, and transmission line properties are provided as model inputs. The trade-offs and synergies among these objectives were visualized for each scenario under multiple environmental flow and power demand requirements. Spatially disaggregated model outputs allowed for the comparison of scenarios not only based on fulfillment of nexus objectives but also scenario compatibility with existing infrastructure, supporting the identification of projects that enhance overall system efficiency. Though the model is applied to the Nepalese nexus from a power development perspective here, it can be extended and adapted for other problems.
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•First study to assess climate change impacts on water availability in KarMo basin.•Climate projection based on an ensemble of a set of RCMs selected rigorously.•Higher rate of ...increase in Temperature in mountains and precipitation in dry season.•Climate change impacts on water are larger at higher altitudes than southern plains.
Karnali-Mohana river basin, Western Nepal.
This study aims to project future climate and assess impacts of climate change (CC) on water availability in the Karnali-Mohana (KarMo) basin. Bias-corrected future climate was projected based on ensembles of multiple models selected from a set of 19 regional climate models (RCMs). The impacts on water availability were then assessed by forcing a well calibrated and validated hydrological model with projected future precipitation (P) and temperature (T) for various climatic scenarios.
Results showed that future T is projected to increase spatio-temporally with higher rate for the mountain stations in the winter season; whereas future P has no distinct spatio-temporal trend but increase in dry season precipitation for future periods. The projected changes in P, T and evapotranspiration are expected to alter average annual flow at the outlets of the KarMo and its sub-basins, albeit with varying rate. The simulated results showed higher impacts in water availabilty at higher altitudes, thus indicating higher vulnerability of northern mountainous region to CC than the southern flatlands. Being the first ever study of such nature in the study area, these results will be useful for planning and development of climate-resilient water development projects in the region.
•First study with adequate spatio-temporal mapping of water resources in KarMo basin.•Hydrological model is developed in SWAT using multi-site calibration approach.•34 % of P is lost as ET; Hill and ...Tarai are relatively wetter than Mountains.•Model is used in assessing E-flows, trade-offs and climate change impacts (Part-B).
Karnali-Mohana (KarMo) river basin, Western Nepal.
This study has developed a hydrological model using multi-site calibration approach for a large basin, the Karnali-Mohana (KarMo) in Western Nepal, which has a lot of potential for water resources development and contribute to the national prosperity. It further applies the model to characterize hydrology and water resources availability across spatio-temporal scales to enhance understanding on water availability and potential uses. The newly developed hydrological model in Soil and Water Assessment Tool (SWAT) is capable of reproducing the hydrological pattern, the average flows, and the flow duration curve at the outlet of the basin and five major sub-basins.
The model simulated results showed that about 34 % of average annual precipitation in the KarMo basin is lost as evapotranspiration, but with a large spatio-temporal heterogeneity. The Hills and Tarai are relatively wetter than the Mountains. The average annual flow volume at the basin outlet is estimated as 46,250 million-cubic-meters (MCM). The hydrological characterization made in this study are further used for climate change impact assessment (Part-B in the same journal), environmental flows assessment and evaluating trade-offs among various water development pathways, which are published elsewhere. This model, therefore, has potential to contribute for strategic planning and sustainable management of water resources to fuel the country’s prosperity.
Systematic mapping assesses the nature of an evidence base, answering how much evidence exists on a particular topic. Perhaps the most useful outputs of a systematic map are an interactive database ...of studies and their meta-data, along with visualisations of this database. Despite the rapid increase in systematic mapping as an evidence synthesis method, there is currently a lack of Open Source software for producing interactive visualisations of systematic map databases. In April 2018, as attendees at and coordinators of the first ever Evidence Synthesis Hackathon in Stockholm, we decided to address this issue by developing an R-based tool called EviAtlas, an Open Access (i.e. free to use) and Open Source (i.e. software code is freely accessible and reproducible) tool for producing interactive, attractive tables and figures that summarise the evidence base. Here, we present our tool which includes the ability to generate vital visualisations for systematic maps and reviews as follows: a complete data table; a spatially explicit geographical information system (Evidence Atlas); Heat Maps that cross-tabulate two or more variables and display the number of studies belonging to multiple categories; and standard descriptive plots showing the nature of the evidence base, for example the number of studies published per year or number of studies per country. We believe that EviAtlas will provide a stimulus for the development of other exciting tools to facilitate evidence synthesis.
Though springs are the primary source of water for communities in the mid-hills of Nepal, an in-depth scientific understanding of spring systems is missing, preventing the design of effective ...climate-resilient interventions for long-term sustainability of springs. This study marks the first attempt to combine environmental isotopes analysis with hydrometric and hydrogeological measurements to identify dominant recharge zones for springs in two mountainous catchments—Banlek and Shikarpur—in Far-Western Nepal. In total, 422 water samples collected from rainfall, springs and streams between March 2016 and March 2017 were analyzed for their isotopic composition (δ
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O and δD). Isotopic composition of rainwater shows seasonality, suggesting that different sources of water vapor cause rains in monsoon and in dry season. Rainfall responses of individual springs were used to identify connections to unconfined and deeper groundwater strata. The isotopic composition of springs in the two catchments ranges from −9.55 to −8.06‰ for δ
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O and −67.58 to −53.51‰ for δD. The isotopic signature of the spring sources falls close to the local meteoric water line for the corresponding season, indicating strong rainfall contribution to springs. Altitudinal isotopic gradients suggest mean recharge elevation of 2,600–2,700 m asl for springs in Shikarpur, which lies beyond the surface-water catchment, and a recharge elevation of 1,000–1,100 m asl for Banlek, which partially extends beyond the surface-water catchment. The demarcated recharge zones will be used by government agencies to implement recharge interventions to increase the resiliency and reliability of springs in Far-Western Nepal.
Abstract
Irrigated wheat production is critical for food security in the Indus basin. Changing climatic and socio-economic conditions are expected to increase wheat demand and reduce irrigation water ...availability. Therefore, adaptation of irrigated wheat production is essential to achieve the interlinked Sustainable Development Goals for both water and food security. Here, we developed a spatial adaptation pathways methodology that integrates water and food objectives under future climate change and population growth. The results show that strategic combinations between production intensification, laser land leveling, and targeted expansion of irrigated areas can ensure wheat production increases and irrigation water savings in the short term. However, no adaptation pathways can ensure long-term wheat production within the existing irrigation water budget under rapid population growth. Adaptation planning for the Sustainable Development Goals in the Indus basin must therefore address both climatic and population changes, and anticipate that current food production practices may be unsustainable.
Introduction
Despite ambitious plans to quadruple hydropower generation in the Indus basin, a quantitative assessment of the impact of climate change on hydropower availability in the basin is ...missing. To address this gap, we combine downscaled CMIP6 projections with the Hydropower Potential Exploration (HyPE) model to quantify future hydropower potential available in the upper Indus basin.
Methods
HyPE uses a spatial cost-minimization framework to evaluate four classes of hydropower potential, namely theoretical, technical, financial and sustainable, considering various constraints on the siting and sizing of two run-of-river hydropower plant configurations.
Results
Under future discharge projections, all classes of potential increase while subbasin changes align with the spatial patterns projected in hydro-climatology. Theoretical potential changes by 3.9–56 %, technical potential by −2.3–46.8 %, financial potential by −8.8–50.4 % and sustainable potential by −6.1–49.7 %. A small decline is observed in the northwestern subbasins where increase in potential is lower than in the southeast. In contrast, with increasing variability in the Indian Summer Monsoon in the future, the southeastern subbasins have the strongest increase in sustainable potential accompanied by higher increase in plant size, decrease in costs and higher variability. The southeastern Satluj subbasin is the hotspot where sustainable potential has the highest increase of up to 145 %. The northwestern Kabul subbasin has the highest decrease of up to −27 %. The Swat subbasin has the lowest variability in sustainable potential while the Jhelum and Indus main subbasins remain the subbasins with the cheapest potential into the future. The performance of future sustainable portfolios differ from the performance of historical portfolios by −11.1–39.9 %.
Discussion
Hence, considering future climate in the present-day planning of hydropower will lead to improved performance under a majority of scenarios. The sufficiency of hydropower potential to fulfill energy security depends on future population growth. Energy availability is projected to decline in the northwest as population increases faster than hydropower potential. The per capita sustainable potential In the Kabul subbasin reduces to a third of the historical value. A socio-hydrological approach is necessary to address the complexity of achieving sustainable and equitable hydropower development in the Indus basin under such spatial mismatch between hydropower availability and energy demand in a resource-limited world.
River systems originating from the Upper Indus Basin (UIB) are dominated by runoff from snow and glacier melt and summer monsoonal rainfall. These water resources are highly stressed as huge ...populations of people living in this region depend on them, including for agriculture, domestic use, and energy production. Projections suggest that the UIB region will be affected by considerable (yet poorly quantified) changes to the seasonality and composition of runoff in the future, which are likely to have considerable impacts on these supplies. Given how directly and indirectly communities and ecosystems are dependent on these resources and the growing pressure on them due to ever‐increasing demands, the impacts of climate change pose considerable adaptation challenges. The strong linkages between hydroclimate, cryosphere, water resources, and human activities within the UIB suggest that a multi‐ and inter‐disciplinary research approach integrating the social and natural/environmental sciences is critical for successful adaptation to ongoing and future hydrological and climate change. Here we use a horizon scanning technique to identify the Top 100 questions related to the most pressing knowledge gaps and research priorities in social and natural sciences on climate change and water in the UIB. These questions are on the margins of current thinking and investigation and are clustered into 14 themes, covering three overarching topics of “governance, policy, and sustainable solutions”, “socioeconomic processes and livelihoods”, and “integrated Earth System processes”. Raising awareness of these cutting‐edge knowledge gaps and opportunities will hopefully encourage researchers, funding bodies, practitioners, and policy makers to address them.
Plain Language Summary
Huge populations of people across Pakistan, India, China, and Afghanistan depend on river systems originating from the mountainous Upper Indus Basin (UIB) region. These river systems are fed by snow and glacier melt and rainfall. However, demand for freshwater is growing due to population growth, industrialization, urban development, etc, and climate change also poses a serious threat to the water supply. These two pressures pose considerable adaptation changes. The strong connections between water resources, climate change, and human activities within this region, therefore, suggest that a multi‐disciplinary research approach combining social and natural/environmental sciences is required for successful adaptation to ongoing and future climate change. Here we use a 'horizon scanning' technique to identify the Top 100 questions related to the most pressing knowledge gaps and research priorities in social and natural sciences on climate change and water in the UIB. Raising awareness of these cutting‐edge knowledge gaps and opportunities will hopefully encourage researchers, funding bodies, practitioners, and policy makers to address them and help inform future water management, climate plans, and development policy in the UIB.
Key Points
The Top 100 research questions on climate change and water in the Upper Indus Basin in the social and natural sciences are identified
Many questions are cross‐disciplinary given the strong linkages between climate, water, and human activities in the Upper Indus Basin
Questions are identified using horizon scanning, which is a technique used to identify knowledge gaps relevant to emerging challenges
The Himalayas are highly susceptible to the impacts of climate change, as it consequently increases the vulnerability of downstream communities, livelihoods and ecosystems. Western Nepal currently ...holds significant potential as multiple opportunities for water development within the country are underway. However, it is also identified as one of the most vulnerable regions to climate change, with both an increase in the occurrence of natural disasters and exacerbated severity and impacts levels. Regional climate model (RCM) projections indicate warmer weather with higher variability in rainfall for this region. This paper combines bio-physical and social approaches to further study and understand the current climate shocks and responses present in Western Nepal. Data was collected from 3660 households across 122 primary sampling units across the Karnali, Mahakali and Mohana River basins along with focus group discussions, which provided a rich understanding of the currently perceived climatic shocks and related events. Further analysis of climatology was carried out through nine indices of precipitation and temperature that were found to be relevant to the discussed climate shocks. Results show that 79% of households reported experiencing at least one type of climate shock in the five-year period and the most common occurrence was droughts, which is also supported by the climate data. Disaggregated results show that perception varies with the region and among the basins. Analysis of climatic trends further show that irregular weather is most common in the hill region, although average reported frequency of irregular weather is higher in the mountain. Further analysis into the severity and response to climatic shocks suggest an imminent need for better adaptation strategies. This study’s results show that a vast majority of respondents lack proper access to knowledge and that successful adaptation strategies must be adapted to specific regions to meet communities’ local needs.
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