Master of Science in Water Resources Engineering & Management

Permanent URI for this collectionhttp://192.248.9.226/handle/123/40

Browse

Browsing Master of Science in Water Resources Engineering & Management by Author "De Silva PKC"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    item: Thesis-Abstract
    Assessment of climate change impact on water availability in upper Mahaweli river basin, Sri Lanka
    (2022) Musadiq F; De Silva PKC
    Climate change, population increase, and economic development will all have an impact on future water availability for drinking water supply, agriculture, and recreation activities, with different effects in different regions. The present study investigates the potential impact of climate change on future water availability in the Peradeniya sub-catchment of the Upper Mahaweli river basin. The hydrological modeling of this study was performed by Hydrologic Engineering Centre Hydrological Modelling systems (HEC-HMS). In this study, the entire catchment area was divided into three sub-basins to simulate runoff at the outlet of the catchment and the model results were calibrated and validated using historical streamflow data. Future runoff based on calibrated parameters was estimated after bias correction of climate rainfall data for representative concentration pathways (RCP) 4.5 and RCP 8.5 scenarios. Further, an assessment of water availability based on annual and seasonal periods was carried out from the model results. The model calibration carried out from 1990 to 1994, indicated good model results in terms of objective functions where root mean square error (RMSE) is 0.60, Nash-Sutcliffe (NSE) is 0.62, and Percent Bias is -15%. Further, validation of model results from 1994 to 2000 yielded RMSE of 0.60, NSE of 0.52, and Percent Bias of 13.9 % indicating good model results. From the results obtained, it was identified that the water availability will increase for both scenarios RCP 4.5 and RCP 8.5 during the mid-century (2040-2060) and end-century (2080-2100) period. The annual water availability concerning the historical period will increase by 27.34 % during the mid-century period and will further increase by 42.06 % during the end-century period in the RCP 8.5 scenario. The seasonal water availability in mid-century compared to the historical period will be more affected during the first inter-monsoon (FIM) period with an average increase of 69 % and 83 % in RCP 4.5 and RCP 8.5 scenario, respectively. Whilst the seasonal water availability will decrease during the first inter-monsoon (FIM) in the endcentury compared to the mid-century period by 26 % and 27 % in RCP 4.5 and RCP 8.5 scenarios, respectively. The findings of this study can be useful for the water managers and stakeholders to manage future water needs in the basin and reduce the future vulnerabilities associated with the increasing water availability in the basin.
  • Thumbnail Image
    item: Thesis-Abstract
    Evaluation of gridded precipitation products for streamflow modelling in GIN watershed, Sri Lanaka
    (2022) Doya PD; De Silva PKC
    Watershed, Sri Lanka An accurate representation of spatial precipitation is significant for hydrological studies. Spatial precipitation is also the basic input for distributed hydrological models and the accuracy of spatial precipitation affects the performance of hydrological models. In many parts of the world, ground-based observation networks are inadequate to capture spatial precipitation because gauge stations cannot be set up anywhere as financial and geographical factors play a vital role in the establishment. To overcome those challenges two existing gridded precipitation data (TRMM and APHRODITE) are used to simulate discharge in the Gin watershed of Sri Lanka. The coefficient of determination improves to 0.78 and 0.65 respectively for TRMM and APHRODITE data after bias correction. While comparing two gridded precipitation data to observed data, the TRMM data shows superior to APHRODITE with the same value of daily and a monthly average rainfall of 11.15 mm and 339.29 mm respectively. The standard deviation shows 21.16 for daily and 167.72 for a monthly scale with the difference of 31.00 % and -0.06 % to observed the data set. The HEC-HMS model is used for generating streamflow from the two gridded and observed data against gauge data. From the other four-parameter (SCS Unit Hydrograph, Simple Canopy, SCS Method, Simple Surface, and Recession) soil moisture accounting parameter calculation was challenging as it has to be carefully determined. The three most sensitive parameters are soil percolation, tension zone storage, and impervious area while the groundwater storage two (GW2) is the least sensitive parameter. Model performance criteria such as RMSE, NSE, and PBIAS are carried out for calibration and validation. The observed data performed good in the simulation of streamflow compared to two gridded precipitation data with an NSE value of 0.70, RMSE Std Dev value of 0.50, and PBIAS of -8.40 % for calibration and NSE value of 0.66, RMSE Std Dev value of 0.66, and PBIAS of -2.34 % for validation. The result shows that the TRMM data is more suitable to be used for hydrological modelling for and water resources management in ungauged areas in Sri Lanka.