Department Of Hydrology Research Articles

Situating the science of disaster risk reduction and management (DRRM) in Nepal for policy and planning

The United Nations Framework Convention on Climate Change (UNFCCC) emphasises the necessity for “more science” in advancing Disaster Risk Reduction (DRR); however, this initiative often falters in developing countries. This paper utilises a situated knowledge framework from feminist science studies to analyse the knowledge institutionalisation pathways of two Scientific Administrative Organisations (SAOs) in Nepal: the Department of Hydrology and Meteorology (DHM) and the Department of Mines and Geology (DMG). These organisations are pivotal in generating knowledge advisories for Disaster Risk Reduction and Management (DRRM). Our findings indicate that knowledge production processes within these institutions are profoundly shaped by their contextual realities. Notably, the understanding of what constitutes “science” for DRR is influenced by the vision and mission statements of the SAOs, which are further informed by national mandates. The study also reveals entrenched knowledge hierarchies and power dynamics that elevate hazard research to “core science,” while relegating social science-based risk assessments to a secondary role. By examining these SAOs, we highlight how SAOs operational context complicates the straightforward demand for “more science”. To address these challenges, we argue for greater visibility of the operational context of these SAOs and emphasise the need to reassess their positioning within the DRR landscape to meet the evolving expectations for risk-based scientific advisories.

Accurate simulation of extreme rainfall–flood events via an improved distributed hydrological model

Recently, the high incidence of extreme rainfall and flood events worldwide has severely harmed regional economies and societies. Therefore, flood simulations and forecasts, which can provide key technical support for regional flood control and disaster reduction, are urgently needed. The Liuxihe model, as a fully distributed, physically based hydrological model, was improved in this study to simulate extreme rainfall flood events in the Beijiang River Basin. This basin is a famous rainstorm centre in Guangxi Province, China. In this work, the Liuxihe model is improved in two aspects: first, its structure and runoff generation and confluence algorithm are improved, and second, the parameter calibration method is optimised. These two adjustments improve the flood simulation performance of the model and reduce the uncertainty of the simulation results. The results revealed that the flood simulated by the improved Liuxihe model was strongly consistent with the measured values, and the index values of the Nash coefficient, correlation coefficient, process relative error, and flood peak flow error performed very well in the scheme evaluation; in particular, the mean process relative error, flood peak error, and peak time difference decreased by 62%, 63%, and 80%, respectively, after model improvement. The error indicators of the simulation were within the allowable error range from the Standard for Hydrological Information and Hydrological Forecasting (GB/T-22482–2008), which meets the accuracy requirements of flood forecasting in the local hydrological department and can be used as a practical operational plan for flood forecasting. These satisfactory flood simulation results showed that the model and algorithm were improved; thus, the improved Liuxihe model can provide important theoretical guidance for regional flood forecasting and flood disaster mitigation.

Climate Change and Flood Vulnerability Analysis in the Narayani River of Nepal

Flood disasters annually devastate livelihoods, particularly during the monsoon season, with no apparent reduction in impacts in low-lying regions of developing countries like Nepal. Given the increasing effects of climate change globally, this study aims to assess climate change effects and biophysical vulnerability of riverine communities to floods in the Narayani River of Nepal, elucidating the interrelationship between these phenomena. This paper presents an analysis of trends and extreme events of climatological variables, such as temperature, precipitation, and daily river discharge and hazard mapping and risk assessments in the river stretch of two Village Development Committees (VDCs) in the country’s inner Terai region of Nawalparasi district for different return-period floods, with the aid of the HEC-RAS (Hydrologic Engineering Centre’s River Analysis System) and HEC-GeoRAS. A long-term climatological data was collected from the Department of Hydrology and Meteorology, Kathmandu, and the analysis was performed using statistical softwares, SigmaStat, and SigmaPlot. In addition, flood conditions representing 2, and 100-year periods were determined using Gumbel’s distribution. The study revealed a narrowing temperature range, with increasing minimum temperatures and decreasing maximum temperatures, precipitation, and river discharge. However, there was a notable increase in extreme events. The hazard mapping indicated the people’s vulnerability to inundation and soil erosion along the low-lying riverbanks. The findings underscore the necessity for reliable technological and socio-economic vulnerability mapping to provide early warnings to at-risk populations. This paper argues that unplanned and mismanaged settlements in riverine areas may lead to population displacements, creating environmental refugees.

Farmers’ Perceptions of the impact of climate change on apple production in lower Mustang, Nepal

Undoubtedly, climate change is becoming a worldwide concern due to its great sensitivity and detrimental effects on livelihood. The government, policymakers, and other relevant stakeholders are striving to come up with novel and innovative approaches to combat the effects of climate change. Nevertheless, understanding and perceptions of the issue among local farmers are more crucial before making mitigation or adaptation plans. It’s them who are actually more exposed to these environmental works and who are on the frontlines of climate change. So, the study was conducted in 2022 at Lower Mustang to understand how farmers perceive climate change, how it has impacted apple production, and to find discrepancies between their perceptions and the actual change in climatic variability recorded by the Department of Hydrology and Meteorology (DHM). Temperature and precipitation were two climatic variables that were taken into account to investigate the significant effects they have on the rate of apple production. Altogether, 60 households from Lower Mustang were selected randomly for the study. Pre-tested interviews, focus group discussions, key informant interviews, as well as secondary data from DHM, the Ministry of Agriculture and Livestock Development (MoALD), etc. were used to collect the required information. The majority of farmers observed an increase in temperature (83.30%) and an unpredictable increase in rainfall (98%), which are consistent with the actual change in temperature and precipitation recorded between 1991 and 2021. Findings show that the average annual temperature and mean annual precipitation are increasing at a rate of 0.012°C per year and 0.4146 mm per year, respectively. This has resulted in the outbreak of significant amounts of diseases and insect pest infestations that have a direct impact on the quality and quantity of apples. The majority of farmers acknowledged that rainfall was the most significant climatic hazards that negatively impacted apple production, followed with hailstones having an impact on apples during flowering and fruiting. Farmers in the study area are limited to intercropping practices, mostly as an adaptation strategy to combat the impacts of climate change. The study concluded that farmers perceived climate change; they are aware of the term ‘Climate Change’ but haven’t taken any significant adaptation measures towards it. So, there is an immediate need for effective adaptation mechanisms, taking into account farmers' perspectives, to make Lower Mustang self-sufficient in apple production.

Examining Varying Rainfall in the different elevation of Nepal and Water Scarcity

This study assesses the variation of rainfall in the different elevations in the water basin in Nepal. Employing time series data sets of rainfall from 1980 to 2020 collected from Department of Hydrology and Metrology, Nepal, this study has used Mann Kendal test and Sen’s test. In the different elevations, the variation of rainfall is heterogeneous. In the steep elevated landscapes, rainfall is extreme. In the last 47 years, trend of annual rainfall’s mean (Rmean) and moving average (Rmeanma) have been declining. During that period, there were extremes of higher and lower rainfall in the decadal time frame. Kendall’s coefficient (τ) and Sen’s coefficient (β) of Rmean are -3.65°c and -0.13°c respectively. It implies decreasing trend of Rmean from 1975 to 2020. Sen’s coefficient (β) of Rmean validate decreasing trend of Rmean. However, it is insignificant (P=0.2>0.05). Differently, except Kendall’s coefficient (τ) and Sen’s coefficient (β) of Rmean in Tzone2 (1990-1999), Kendall’s coefficient (τ) and Sen’s coefficient (β) of the remaining three time zones, Tzone1 (1980-1989), Tzone3 (2000-2009) and Tzone4 (2010-2019) are negative. Therefore, rainfall has negative trend in the different elevations of the water basin. We conclude water scarcity & stress exist in the small cities. To minimize water vulnerability, water saving and preserving behaviour of household should be developed and the government agency should campaign tree plantation, protect water sources and initiate water management program.

Climate change and adaptive strategies for agriculture in Panchkhal Municipality

Climate change is a modern global crisis caused by human activities that emit greenhouse gases and alter the Earth's natural systems. It is now an undeniable global burning issue, affecting the complex relationship between the physical landscape, natural resources, and how communities adapt to the effects of climate change. Climate change brings many uncertainties to the livelihoods of farming communities that depend on weather and climate. The purpose of this paper is to examine the climate change and adaptive strategies of the farmers in Panchkhal Municipality using an explanatory mixed-methods research design. Primary data were collected from field observation, questionnaires, and interviews. Secondary data were collected from the Center Bureau of Statistics (CBS) and the Department of Hydrology and Meteorology (DHM). The finding shows the many impacts of climate change, such as hot waves, floods, landslides, droughts, increased diseases in agriculture production, and drying up water resources. Similarly, it shows that traditional adaptive strategies have been changing due to a decline in food crop production over the last two decades. Thus, strong policy efforts need to be prepared to mitigate the adverse impact of climate change on traditional farming methods.

River channel dynamics and flooding: A case of motorable bridge collapse due to abrupt flood in Chhabdi Khola, Tanahun, Nepal

The monsoon season in Nepal brings calamitous events like riverbank erosion, toe cutting, and the structural failure of bridges due to floods. In July 2021, a motorable bridge in Bhadgaun, Tanahun district, Nepal, collapsed during a massive flood in Chhabdi Khola. The study aims to comprehensively document the aftermath, specifically focusing on the causal factors that led to the damage of the Chhabdi Khola Dovan Bridge. The study delves into an in-depth analysis of the stream's channel morphology, with the 5.85 kilometers Chhabdi Khola partitioned into 28 distinct segments, each spanning approximately 200 meters. These segments, sequentially labeled from Site 1 to Site 28, encompass the area extending from the upstream at Chhabdi Barah temple to the downstream at bridge’s location. Rigorous measurements of length, breadth, and depth at each site form the basis for volumetric assessments of the stream. The study revolves around contrasting paleo channel attributes with contemporary alterations within the Chhabdi Khola catchment. The analysis leverages precipitation data sourced from the Department of Hydrology and Meteorology (DHM) to discern precipitation trends within the Chhabdi Khola catchment area. The hydrographic data underwent trend analysis utilizing Mann-Kendall and Sen's slope method through R software (version 4.3.2). The collapse of the Chhabdi Khola Dovan Bridge resulted from intense water flow and debris due to heavy rainfall and a narrow outlet near the bridge, impacting the local population and land users facing the enduring aftermath of a catastrophic monsoon event. The study highlights the significance of understanding river dynamics in small streams and advocates for proactive disaster preparedness measures, even in seemingly small river channels.

How Effective Is Inter-Basin Transfer to Manage Temporal Variation Of “Too Much” And “Too Little” Water Conditions for Irrigation in a Himalayan Basin?

Better irrigation facilities leading to “more crop per drop” are today’s needs. This study examines how the overall water balance of Sunkoshi, Marin, and Bagmati Basins will be altered by implementing the Sunkoshi-Marin Diversion Project (SMDP) to fulfill the unmet demands of the Bagmati Irrigation Project (BIP) in the Bagmati Basin via the Marin Basin in Nepal. The specific objectives are to: i) quantify “too much” and “too little” water peculiar to the study basin based on historical data; ii) evaluate water availability, irrigation water requirement, and deficits with and without SMDP; and iii) provide evidence-based recommendations on the effectiveness of the SMDP considering hydropower generation, irrigation and low- and high-flow conditions. Thirty years of historical daily flow data (two gauging stations) and precipitation data (15 stations) were obtained from the Department of Hydrology and Meteorology. Other spatial input data were acquired from relevant authorized sources. Water availability has been estimated using flow at the diversion sites while the irrigation requirements have been calculated based on secondary information. Results show that additional water is not at all required for Marin and Bagmati Basins in the monsoon season. Rather, the diverted water increases the flood hazard. Moreover, the contribution of hydropower from SMDP to the national energy demand is insignificant in the monsoon. However, the SMDP was found to play an important role in meeting the irrigation deficits during the dry season. Its contribution to hydropower production in the lean period is also commendable. However, the proposed irrigation requirement of the BIP cannot be met even after the implementation of the SMDP. More importantly, there is a high probability of the intended diversion flow not being available in the Sunkoshi River (donor) which could have severe consequences downstream. Therefore, additional options for conjunctive use need to be explored.

Study of Climatic Pattern and Water Resources from Citizen Science’s Perspective in Namobuddha Municipality, Kavre, Nepal

This study has been initiated to carry out the research on climatic patterns along with water resources from local communities’ perspectives in Namobuddha Municipality, Kavre, Nepal. The study area is located in the eastern part of Kathmandu which is about 35 km away from it. This study has focused on investigating climatic patterns and water resources available in the study area. It was especially carried out utilizing citizens’ perspectives. Mixed qualitative and quantitative methods were used in this study. Total 66 questionnaire surveys and two key informant interviews were conducted in the Simalchaur Sympati area of Namobuddha Municipality which has about 600 households. Required Meteorological data were taken from the Department of Hydrology and Meteorology, Nepal. Results from this study showed that the average, minimum and maximum temperatures were in the increasing trend. However, the average annual along with the monsoon rainfalls were in the decreasing trend. The inhabitants have experienced warmer summer and winter, scarcity of water for domestic as well as for agriculture purposes. Local communities also deplored less ground water flow in their springs. This study has clearly signified the drying up of surface and ground water resources. In overall context, this study output was similar to the global pattern as temperatures are in increasing trend whereas precipitation is in decreasing trend. It signified the need for effective adaptation strategies to combat against the adverse impacts of changing climatic patterns especially for the management of water resources in the study area.

Climate change and infectious disease surveillance in Nepal: qualitative study exploring social, cultural, political and institutional factors influencing disease surveillance.

To explore the impacts of contextual issues encompassing social, cultural, political and institutional elements, on the operation of public health surveillance systems in Nepal concerning the monitoring of infectious diseases in the face of a changing climate. Semi-structured interviews (n=16) were conducted amongst key informants from the Department of Health Services, Health Information Management System, Department of Hydrology and Meteorology, World Health Organization, and experts working on infectious disease and climate change in Nepal, and data were analysed using thematic analysis technique. Analysis explicates how climate change is constructed as a contingent risk for infectious diseases transmission and public health systems, and treated less seriously than other 'salient' public health risks, having implications for how resources are allocated. Further, analysis suggests a weak alliance among different stakeholders, particularly policy makers and evidence generators, resulting in the continuation of traditional practices of infectious diseases surveillance without consideration of the impacts of climate change. We argue that along with strengthening systemic issues (epidemiological capacity, data quality and inter-sectoral collaboration), it is necessary to build a stronger political commitment to urgently address the influence of climate change as a present and exponential risk factor in the spread of infectious disease in Nepal.

Effect of Surface Characteristics and Rainfall in Infiltration Rate: A Case Study of Kaligandaki River Basin

Study of infiltration characteristics is crucial for effective watershed management, as it helps determine the water availability for crops, the need of irrigation, groundwater recharge, and surface runoff. This study is aimed at identifying the relation between infiltration rate and surface characteristics as well as rainfall rate in the Kaligandaki River basin of Nepal using Hydrologic Modelling System (HEC-HMS). HEC-HMS is a physically based, semi-distributed model that uses the weather and spatial information of soil and landuse of the basin for deriving the inputs for the model. A hydrological rainfall-runoff model is developed for the Kaligandaki River basin, with outlet at hydrological station 420, Kotgau, of Department of Hydrology and Meteorology (DHM). The model was then validated at DHM station 420, Angsing, of Kaligandaki River. Model generated subbasin wise infiltration rates and existing landuse were analysed and it was found that sub-basins with dominant landuse as forest had high infiltration rate among prevailing landuse types. Conversely, low infiltration rate was observed for barren area, snow/glacier and grassland landcover type dominated subbasins. A positive correlation among rainfall rate and infiltration rate was seen with linear increase in infiltration rate for an exponential increase of average rainfall intensity. Infiltration rate was found to have positive correlation with the Hydrologic Soil Group types as suggested by NRCS. Moreover, the study signified a greater impact of landcover over soil types on infiltration rates. Whereas, no significant impact of basin slope on infiltration rate could be identified, which may be due to preclusion of multiple topographic features. Understanding the impacts of rainfall intensity and surface characteristics on infiltration enables proactive measures to mitigate the issues like landslide and reduce flooding and soil erosion by improving infiltration rates through surface condition assessment.

Rain Fall Prediction using Ada Boost Machine Learning Ensemble Algorithm

Every government takes initiative for the well-being of their citizens in terms of environment and climate in which they live. Global warming is one of the reason for climate change. With the help of machine learning algorithms in the flash light of Artificial Intelligence and Data Mining techniques, weather predictions not only rainfall, lightings, thunder outbreaks, etc. can be predicted. Management of water reservoirs, flooding, traffic - control in smart cities, sewer system functioning and agricultural production are the hydro-meteorological factors that affect human life very drastically. Due to dynamic nature of atmosphere, existing Statistical techniques (Support Vector Machine (SVM), Decision Tree (DT) and logistic regression (LR)) fail to provide good accuracy for rainfall forecasting. Different weather features (Temperature, Relative Humidity, Dew Point, Solar Radiation and Precipitable Water Vapour) are extracted for rainfall prediction. In this research work, data analysis using machine learning ensemble algorithm like Adaptive Boosting (Ada Boost) is proposed. Dataset used for this classification application is taken from hydrological department, India from 1901-2015. Overall, proposed algorithm is feasible to be used in order to qualitatively predict rainfall with the help of R tool and Ada Boost algorithm. Accuracy rate and error false rates are compared with the existing Support Vector Machine (SVM) algorithm and the proposed one gives the better result.

Performance Assessment of Chirps, Persiann – CDR, IMERG, and TMPA Precipitation Products across Nepal

The observation of hydrological as well as meteorological data is very essential for any kind of hydraulic and hydrological study. In Nepal, due to the significant variation of topography and climatic characteristics as well it is necessary to establish the meteorological stations densely, here only 231 meteorological stations are available and are handled by government organizations Department of Hydrology and Meteorology (DHM). Even though, due to many limitations, the satellite data is very useful for the water resources study. There are so many satellite products available but the performance of these products varies from place to place. In this study, the performance of four satellite products i.e., Climate Hazards Group Infrared Precipitation with Station data (CHIRPS), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN-CDR), Integrated Multi-Satellite Retrievals for GPM (IMERG), and TRMM Multi-satellite Precipitation Analysis (TMPA) all over Nepal are evaluated with different elevation bands. The performance of each product is evaluated by Probability of Detection (POD), Critical Success Index (CSI), Frequency Bias Index (FBI), False Alarm Ratio (FAR), Root Mean Square Error (RMSE), and Percentage Bias (PBIAS). After analysis of each product, the PERSIANN-CDR data set gives a reasonable performance for all elevation bands after bias correction.

Forecasting Climate Variability in Nepal

Climate variability is noted a critical issue in Nepal. This paper investigates empirically and analytically whether climate variability exists or not in different altitudes, whether its direction moves and what will be its future direction. In this study, we used a time series forecasting model based on the secondary data of hydrology and metrology collected from the Department of Hydrology and Metrology, the Government of Nepal. As a result, this paper found climate variability in the different parts of Nepal where variations of climatic variables (temperature and rainfall precipitation) are found all months of the year. In the estimation, on average temperature rising per annum is by 20 C from 1975 to 2012. However, declining rainfall per annum was noticed. Additionally, the estimated forecasting of temperature variation over the next 40 years would be 60c over. In the case of rainfall forecast, it would be constant and results from drought at high altitude and flood at low altitude. Therefore, climate variability may be a big threat in the next 40 years across the country, of Nepal. The result may be valuable input to the policymakers and farmers for economics as usual.

TREND ANALYSIS ON CLIMATE VARIABILITY IN KATHMANDU VALLEY

The study of temperature and rainfall spatiotemporal dynamics is critical for assessing climate change. The current changes are distinctly more rapid and not due to natural causes but by anthropogenic activities. Various studies suggest that Kathmandu is one of the urbanized and polluted cities in Nepal. The main objective of this study was to assess the trend of climate in Kathmandu. This study was based on climatic data. It utilized the data from the Department of Hydrology and Meteorology between 1991- 2020 based on Pani-Pokhari stations. Similarly, secondary data were collected from relevant literature including reports, journals, websites, and publications. linear regression analysis was performed to determine the climatic variability of the study area. The result showed that the year-wise precipitation trend was increasing at the rate of 0.07mm per year with rainfall distribution in the month of July. The seasonal trend analysis of precipitation shows that the rainfall was increasing during Monsoon and Winter while decreasing in the case of Pre-monsoon and Post- monsoon. There was an increase in both the minimum and maximum temperature at the rate of 0.0424°C/year and 0.1047°C/year respectively. The average temperature increased in the Summer and Winter seasons. Both maximum temperatures, as well as minimum temperatures, were increasing. Though the change is small, it takes no time to turn into a big one and create a serious impact on different sectors. So, immediate adaptive, as well as mitigating measures, should be taken to reduce the impacts of climate change in Kathmandu valley.

Effect of Different Irrigation Patterns on Oat-Vetch Mixed Forage Production System in Rasuwa, Mid Hills of Nepal

Abstract: The scarcity of forage resources, particularly in Nepal's midhills, poses a challenge to the sustainable development of livestock production. In order to address issues, an experiment was carried out in 2020 at Kalika Municipality in Rasuwa District, Nepal, to determine the best forage combinations in terms of total dry matter productivity. With irrigation as a main plot effect, a 4*3 factorial RCB design was used with four replications. Crop species included oat (Avena sativa, Kamdhenu), common vetch (Vicia sativa), and combinations of oat and vetch within a sub plot. Irrigation treatments included none, once per month (30-day interval), twice per month (15-day interval), and three times per month (10-day interval). Temperature and precipitation data from nearby stations were taken from the Department of Hydrology and Meteorology. The first harvest was taken after 65 days of sowing (DAS), with consecutive harvests after 35 days of the initial harvest. The experimental findings revealed that the first, second, and total dry matter production were altogether found highest in the three times irrigated plot (2.47±0.25, 1.38±0.21, 3.85±0.46 respectively) and lowest in the rainfed condition (1.37±0.22, 0.69±0.12, 2.07±0.33 ton/ha respectively) with statistically highly significant result (p<0.001). The oat and vetch mixed cropping pattern had statistically higher dry matter production in the first (2.66 0.14 ton/ha), second (1.5 0.13 ton/ha), and overall average total production of (4.16 0.25 ton/ha), among the subplot effect (species). Additionally, among the subplot effects, the oat and vetch mixed cropping had the highest dry matter production in terms of first harvest yield, regrowth, and overall yield (p<0.01). Oat sole cropping could be replaced with mixed cropping of oat and vetch at a ratio of 50:50 (50:10 kg ha-1) because it produced the highest yield advantage, including forage quality. These findings provide scientific support for common vetch-oat intercropping as a sustainable approach to increase forage production with 10-day irrigation interval. These mixtures appear promising for the development of sustainable crop production with low external input and higher economic yield, and they can be used as a viable option by farmers in rainfed mid-hills of Nepal

УКРАЇНСЬКА НАУКОВА ГІДРОЛОГІЧНА ТЕРМІНОЛОГІЯ: ІСТОРІЯ ФОРМУВАННЯ, СУЧАСНИЙ СТАН ТА ПРІОРИТЕТИ РОЗВИТКУ

The purpose of this article is to acquaint the general public of scientists, educators and practitioners who work in the field of hydrology, use and protection of surface waters of the land with the formation and development of Ukrainian scientific terminology, as well as the developments in this direction of research during the period of independence of Ukraine, which were carried out in the Ukrainian Hydrometeorological Institute the Institute of the State Emergency Service of Ukraine and the National Academy of Sciences of Ukraine and at the Department of Hydrology and Hydroecology of the Faculty of Geography of Taras Shevchenko Kyiv National University. The history of the formation of Ukrainian scientific hydrological terminology over the last more than 150-year period largely reflects the complex historical process of the formation of Ukraine as an independent state. Despite the difficulties of development at certain historical stages, terminological activity on the territory of modern Ukraine developed, acting as a powerful factor in the establishment of its own style of Ukrainian scientific language, which can satisfy the demand of a wide range of scientists and practitioners working in the field of studying, using and protecting surface waters. In Ukraine, teams of scientists and educators have formed, which have significant achievements in the development of Ukrainian hydrological terminology. It is important not to neglect this direction of research in the future. This especially applies to the implementation of terms in practical activities. Among the measures that can contribute to this, it is possible to name the inclusion of issues of hydrological terminology in the programs of scientific and scientific-practical events held in Ukraine on water issues, as well as programs of course events for improving the qualifications of specialists working in enterprises, institutions and organizations of the hydrometeorological service, water management, environmental protection. The article was prepared based on the results of the authors’ work on the development of hydrological normative, educational and scientific reference literature, as well as the study of relevant Ukrainian and foreign literary sources. Achievements, problematic issues are shown, and priority tasks for development in this direction of research are outlined.

Rainwater Harvesting Practices and Its Effectiveness in Kathmandu Metropolitan City

Water scarcity has been a major problem of Kathmandu Metropolitan City (KMC). Different interventions are being attempted to solve this problem including the highly discussed Melamchi Drinking Water supply project. Thus, so rainwater harvesting (RWH) could be a promising approach to satisfy water to some extent. The study has aimed to assess the status of rainwater harvesting practices in KMC and to examine its effectiveness in overcoming the water shortage. A total of 244 households were surveyed covering 32 wards of KMC through random sampling method and semi structured questionnaire forms were laid for the data collection. The annual rainfall data of interval 30 years (1990-2019) of KMC, collected from department of Hydrology and Meteorology for trend analysis. Study revealed 58.2% of households are practicing RWH and among them 63.2% installed RWH system more than five years ago. About 63% of households are practicing roof top harvesting which is found to be more convenient in terms of cost and space. Strong positive correlation (R2=0.876, r=0.942) was observed among amount of water harvested and space occupied by RWH system and was statistically significant (P <0.05). Harvested water is found mainly used for household’s chores, flushing toilets and watering the garden. Majority (95.8%) of respondents did not prefer harvested water for drinking due to its poor water quality, high contamination and bad odor and taste. About 73.2% of the respondents decontaminate harvested water before using and filtration (63%) is found to be most common and effective method for decontamination. Despite of challenges like leakages of storages and gutters, about 87.3% of respondents are strongly satisfied with RWH system as it reduced the municipal water supply bill and provides excess water for the sanitation. Furthermore, the trend analysis showed increment of rainfall in the area by 1.21 mm per annum. Study regarding governmental incentives for the installation of RWH system, availability and accessibility of quality products, training on installation and sanitary management of RWH system would help to shed further light in the aspects of RWH.

Changing Rainfall Pattern in Pokhara Valley, Nepal


 
 
 Pokhara valley lies on the southern slope of the Annapurna Range in the Himalayas, Nepal. The mountain range blocks the monsoon originating from the Bay of Bengal in the monsoon season. Based on the observed rainfall data from 1991 to 2021 AD from the Department of Hydrology and Meteorology (DHM), Government of Nepal (GoN), this study aims to assess the monthly, seasonal, and annual pattern of rainfall in Pokhara. Trend analysis for annual rainfall as well as seasonal and monthly rainfall was performed and a regression method was used to find the rate of increase or decrease of the rainfall. Pre- monsoon and monsoon seasons indicate both an upward and a downward trend, whereas post-monsoon and winter seasons illustrates the exact opposite. However, the average monthly rainfall indicates an upward trend, despite the fact that the annual rainfall exhibits both an increasing and a decreasing trend. According to the research, there are rising (+ve) and falling (-ve) trends for the different stations. Although both stations are very near, the precipitation varies broadly. Such massive variation within the short distance might be due to climate change, local wind effects, outflanking of hydraulic structures, and monsoon patterns.
 
 

Impact of Variation in Monsoonal Rainfall and Temperature on Paddy Production and its Adaptive Strategies: A Case Study from Bhaktapur District of Nepal

This study was carried out to assess the impact of climate change on paddy yield in Bhaktapur, Nepal. The study compared the summer rainfall variability, summer temperature variability, and farmers' perception of rainfall and temperature changes over a 30-year period. A household survey of 420 houses was conducted to collect information supplemented by meteorological data from the Department of Hydrology and Meteorology (DoHM). Following this, significant increases and decreases in temperature and rainfall were observed on annual and seasonal time scales, respectively. The obtained result shows the annual precipitation trend of the study area is increasing at a rate of 0.24 mm yr-1. The linear trend analysis of the pre-monsoon indicates that the rainfall is increasing at the rate of 0.18 mm yr-1 and the monsoon shows the rainfall is increasing at the rate of 0.57 mm yr-1, whereas the post-monsoon rainfall is decreasing at the rate of 0.02 mm yr-1. The biggest changes in precipitation were observed during the monsoon season. The monsoon precipitation trend in the time series was found to be increasing at a rate of 0.57 mm yr-1. This variation in monsoon rainfall is clearly unfavorable for the agriculture system of the study area. When these recent changes in the temperature and precipitation were compared over 30-year time series data from the weather station, it is apparent that the climate of the study area exhibits fluctuation over time, many of the changes being very erratic. As per the data, all kinds of temperatures are being increased annually. According to the linear trend shown below, average annual temperature, minimum temperature, and maximum temperature are increasing at rates of 0.038°C yr-1, 0.054°C yr-1, and 0.021°C yr-1, respectively. The results show that future climate change in Nepal, including higher temperatures and erratic rainfall, might have a negative impact on paddy productivity and yield in the study area.