Mohammed Sharif

Generation of Daily and Hourly Weather Variables for use in Climate Change Vulnerability Assessment

This paper evaluates the impact of climate change, as projected by two Global Climate Models (GCMs) on the occurrence of extreme precipitation events in the Upper Thames River Basin in the Canadian province of Ontario. The modelling approach presented herein involves a two-stage process of generating daily weather data followed by disaggregation to an hourly time step of select variables for some events. Monthly change fields for three weather variables (maximum temperature, minimum temperature, and precipitation) were obtained from the output of two GCMs. The historical data set is modified by applying change fields to the weather variables simultaneously and then using this as the driving data set for an improved K-nearest neighbour weather-generating model. Weather sequences representative of climatic conditions in 2050 were simulated. Disaggregation of precipitation data is carried out using a new method that is a hybrid key site approach. A distinct practical advantage of the approach presented here is that extreme wet and dry spells are simulated, which is crucial for evaluation of effective flood and drought management policies for the basin.

Flood risk management strategies for national capital territory of Delhi, India

Abstract Delhi, a mega city with a population of 16.78 million, is situated on the bank of River Yamuna. During the last three decades, the hydrological characteristics of the Yamuna River basin have significantly changed. Due to rapid urbanization in the basin, the runoff has considerably increased. Consequently, the flooding events are now occurring more frequently and with higher magnitudes. A sizeable population of the city of Delhi resides in settlements that have mushroomed in the flood plains of Yamuna. A majority of these settlements is in the low-lying areas, which make them highly vulnerable to flooding events of even moderate intensity. In the present paper, several structural and non-structural measures for the management of flood risk in the national capital territory of Delhi have been recommended. A critical analysis of the existing flood control measures has revealed several shortcomings. Based upon the analysis, several implementable structural and non-structural measures for alleviating the problem of riverine as well as urban flooding in the national capital territory of Delhi have been recommended. Proper implementation of the recommended structural and non-structural measures could significantly reduce the flood risk associated with riverine and urban flooding in the national capital territory of Delhi.

Trends in Streamflow Magnitude and Timings in Satluj River Basin

Most operational decisions for water resources infrastructure are dependent on both the timing and magnitude of flows, and therefore climate change impact assessment must consider both these characteristics. This paper examines trends in the magnitude and timings of streamflow at several stations in Satluj River basin in India. The intention is to increase the reliability of water resources systems in the basin through consideration of the observed trends. The Mann-Kendall nonparametric trend test, incorporating a correction for serial correlation and presence of ties, was used for the detection of trends. Trends in seasonal proportions of annual flow as well as actual flows have been investigated. Timings of extreme flows at several locations in the basin have also been investigated. The results reveal more trends than would be expected to occur by chance for several of the magnitude and timing measures considered in this study. The contribution of glacier melt to annual runoff at Bhakra, the major reservoir in the basin, is approximately 59% and therefore any changes in magnitude and timings of water availability at the reservoir could have significant implications for its operation. Further, climate change induced changes in the timings and magnitude of water availability at Bhakra, the major reservoir in the basin, could put the drinking water supplies of millions of people at risk. The study will contribute towards climate change modeling efforts being undertaken in a climatologically sensitive basin such as Satluj.

Flood estimation at Hathnikund Barrage, River Yamuna, India using the Peak-Over-Threshold method

ABSTRACT The paper presents a methodology for the estimation of flood magnitude using the peaks-over-threshold (POT) data. A semi-automatic approach for the determination of POT values has been presented. Two frequency analysis methods, namely Gumbel’s method and Log-Pearson type III distribution, have been used. Two major issues in implementing a POT approach are: (i) determining an appropriate threshold and (ii) ensuring the independence of events. The present paper addresses these issues simultaneously. Using the daily discharge data, various return-level flood magnitudes have been estimated. A comparison of flood magnitudes obtained using the annual maxima (AM) approach and POT approach clearly indicates that the flood magnitudes in general are higher when Log-Pearson method is used as compared to when Gumbel’s method is used. The result of the research conducted clearly indicates that the flood magnitudes estimated on the basis of POT sample are more reliable, particularly when the data length is short.

Assessment of climate change impacts on streamflows in Satluj river basin, India using SWAT model

This paper describes the development and application of soil and water assessment tool (SWAT) to the simulation of stream flows at Bhakra - the major reservoir in the Satluj River basin in India. The basin lies in the Himalayan region, which is one of the most climatically sensitive areas in the world. PRECIS generated outputs of climate variables under IPCC A1B Scenarios for Indian conditions corresponding to the baseline (1961-1990), midcentury (2021-2050) and endcentury (2071-2098) have been used as an input to SWAT model. Results of simulation indicate that mean annual streamflows at Bhakra will likely increase by 12.8% for the midcentury, and 19.4% for the endcentury in response to climate change projections generated using PRECIS. For the January-February period, the streamflows are projected to increase by 49% for the midcentury and 21% for the end century relative to the base period. For the monsoonal season, both the midcentury and the endcentury periods are projected to experience an increase in streamflow of around 10% relative to the baseline period. The present study provides guidance in the understanding of climate change impacts on the hydrologic regime in a basin that is highly vulnerable to the impacts of climate change.

Extreme precipitation events simulation under plausible scenarios of climate change in Satluj River basin, India

A K-nearest neighbour weather-generating model is applied to simulate: 1) total precipitation during extreme precipitation events; 2) duration of extreme wet spells; 3) duration of extreme dry spells in the Satluj River basin - a key basin in the central Himalayas under climate change scenarios projected by 15 different combinations of global climate models (GCMs) and emission scenarios. The intent is to assess the vulnerability of the basin to extreme hydrological events, including floods and droughts, resulting from extreme precipitation events. The driving data set for the K-NN model was obtained by applying the precipitation change fields obtained from different combinations of the GCM and emission scenarios to the observed data. Results indicate that several extreme wet and dry spells that were more severe than the observed were simulated. Results of frequency analysis of storm depths indicated that ECHAM5 model under A2 scenario produced the highest one-day precipitation maxima for each return period considered.