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    Discrete wavelet-Ann approach in time series flow forecasting-a case study of Brahmaputra river
    (2012) Deka, P.C.; Haque, L.; Banhatti, A.G.
    This paper deals with the prediction of hydrologic behavior of the runoff for the one of the largest discharge carrier International River, Brahmaputra, located in Assam (India) at the Pandu station, by using daily time unit. The flow regime dominated by high data non-stationary and seasonal irregularity due to Himalayan climate fallout. The influence of data preprocessing through wavelet transforms has been investigated. For this, the main time series of flow data were decomposed to multi resolution time series using discrete wavelet transformations. Then these decomposed data were used as input to Artificial Neural Network (ANN) for multiple lead time flow forecasting. Various types of wavelets were used to evaluate the optimal performance of models developed. The forecasting accuracy of the models has been tested for multiple lead time upto 4 days using different decomposition levels. The performance of the proposed hybrid model has been evaluated based on the performance indices such as root mean square error (RMSE), coefficient of efficiency (CE) and mean relative error (MRE).The results shows the better forecasting accuracy by the proposed combined hybrid model over the single ANN model in hydrological time series forecasting. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.
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    Evaluating uncertainty of the soil and water assessment tool (SWAT) model in the upper cauvery basin, Karnataka, India
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2015) Kumar Raju, B.C.; Nandagiri, L.
    Quantification of uncertainties associated with hydrological models are essential for accurate assessment of water balance components and optimal planning and management of water and land resources at basin-scale. The present study was taken up to evaluate the uncertainties associated with the Soil and Water Assessment Tool (SWAT) model using for two different techniques: i) Generalized Likelihood Uncertainty Estimation (GLUE) and ii) Sequential Uncertainty Fitting (SUFI-2) techniques. The study was carried out in the Upper Cauvery River basin (36,682 km2) located in the humid to sub-humid region of Karnataka State, India. The calibration of the model was carried out using the Nash – Sutcliffe (NS) coefficient as the objective function for both GLUE and SUFI-2 techniques. The P-factor was 67% and 71% of observed streamflow data bracketed by the 95% prediction uncertainty (95PPU) for GLUE and SUFI-2 respectively during calibration period and corresponding values of 54% and 61% during validation period. Overall results indicate the applicability of SWAT model with moderate levels of uncertainty in large basins located in the humid tropics. The calibrated SWAT model can be used for assessment of water balance components and land use management scenarios in the Upper Cauvery Basin. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Streamflow response to land use-land cover change over the Nethravathi River Basin, India
    (American Society of Civil Engineers (ASCE), 2015) Babar, S.; Ramesh, H.
    Land use-land cover change (LULC) has considerable impacts on hydrologic response at the watershed level. Quantitative assessment of LULC impacts on runoff generations is vital for water resources development. The soil and water assessment tool (SWAT) model was used to study the effect of LULC change on streamflows. In addition to this, the present study proposed a newly developed flow-routing model called runoff coefficient routing model (RCRM). This new model is simple and requires limited data, such as precipitation, LULC and streamflows as compared to other models, which require meteorological and many more input data. The Nethravathi River basin was selected for testing the RCRM model with the SWAT model to study land use-land cover change on streamflows. The SWAT model and RCRM model have been calibrated for 2001-2005 and validated for 2006-2009 daily data. Results have shown that the simulated streams are well correlated with observed streamflows with a coefficient of correlation (R2) equal to 0.82 in calibration and 0.68 in validation period. Whereas, the RCRM model results have shown R2 of 0.81 and 0.66 in the calibration and validation period. Finally, the SWAT and RCRM results were compared. It is observed that the results of the RCRM model have shown a good agreement with SWAT model results of R2 equal to 0.99 and 0.98, respectively, in the calibration and validation period. The sensitivity analysis was also carried out based on Latin hypercube one factor-at-a-time (LH-OAT) method using the SWAT model and found 11 sensitive parameters out of 28 parameters. Model performance was carried out using the Nash-Sutcliffe model efficiency coefficient (NSE) and found 0.81 for calibration and 0.62 for the validation period in the SWAT model. RCRM has NSE of 0.79 and 0.63. The response of the streamflows for the year 2013 was simulated from the calibrated model. The results showed that the observed streamflows have shown good correlation with simulated streamflows with R2 values of 0.86 and NSE of 0.81. From the results, it is concluded that the runoff shows early response in the year 2013 compared to the year 2003. This is mainly due to changes in LULC, which shows the conversion of forest to agricultural area and increase in built-up area from 2003 to 2013. The effect of LULC change on the hydrological model parameters were calculated and observed a decrease in evapotranspiration (ET) of about 4.5%, an increase in runoff of about 0.9%, and an increase in groundwater of about 1.12%. In conclusion, the proposed RCRM in the present study simulates streamflows at par with the SWAT model with only few input data. Hence, the newly developed RCRM model would be used to study streamflows responses to LULC changes. © 2015 American Society of Civil Engineers.
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    Hydrological effects of land use /land cover changes on stream flow at Gilgel Abay River Basin, Upper Blue Nile, Ethiopia
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Mulu, A.; Dwarakish, G.S.
    Water is the most important resource for the survival of living things and it is the most essential resource associated with land use/ land cover (LU/LC) changes. Therefore, it is very important to make evaluations of the expected impact on the hydrology and water resources due to expected changes. The main objective of this study is to assess the hydrological effect of land use/ land cover changes on stream flow at GilgelAbay river basin using Precipitation Runoff Modeling System (PRMS) model. System inputs are daily time-series values of precipitation, minimum and maximum air temperature, and parameter files which are generated from GIS Weasel. To identify effect of changes in LU/LC, vegetation type and vegetation density on stream flow, LU/LC, vegetation type and vegetation density data from 1990-2000 and 2001-2010 years were considered. This different period LU/LC, vegetation type and vegetation density with soil data and DEM were given to GIS Weasel to generate different parameters for PRMS model. These generated parameters together with time series data (daily minimum and maximum air temperature, daily precipitation and daily stream flow) feed to PRMS model to simulate stream flow for the years 1993-2000 and 2001-2008. From the time series data, climate changes (daily maximum and minimum temperature and daily precipitations) were kept the same as baseline period (1993-2000). The stream flow of 2001-2008 compared with baseline period (1993-2000) and the effect of LU/LC, vegetation type and vegetation density was identified using calibrated and simulated PRMS model. Hence, as LU/LC, vegetation type and vegetation density changed from 1993-2000 period to 2001-2010 period, stream flow increased from 7.8% (128.4 Mm3) to 25.3% (432 Mm3) and ET decreased from 4.2% (75 Mm3) to 20% (524 Mm3) from baseline period. For the whole simulation periods (2001-2008) stream flow increased by 10.9% (784 Mm3), but ET decreased 6.7% (43 Mm3) related to baseline periods. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Analysis of climate trend and effect of land use land cover change on Harangi streamflow, South India: a case study
    (Springer Science and Business Media Deutschland GmbH, 2017) Anil, A.P.; Ramesh, H.
    Land use land cover (LULC) and climate change are considered to be driving factors contributing to the alteration of the hydrological regime. Therefore, an attempt has been made to study climate trend and the effect of LULC on streamflow in a basin covered predominantly by forest. The Harangi river basin is one of such basins located in the western ghats of South India. The LULC trend was carried out by considering temporal multispectral data for the years 1990, 2002 and 2008 obtained from Landsat-5TM and IRS 1C (Indian Remote Sensing Satellites). Climate parameters such as rainfall and temperatures were considered for the trend analysis in this study. The rainfall trend was studied using Man-Kendall and Sen’s slope method to understand the spatio-temporal variability. Rainfall shows the decrease trend at Suntikoppa rain gauge station in January and June months. Harangi and Madapura rain gauge stations also show a decrease of rainfall trend for only January month. Temperature trend show increase in maximum temperature for the month of April, May and November whereas increase in minimum temperature was observed in the month of November and December. Spatial extent of LULC found that 52.4% (220.014 km2) of the study area was covered with forest in 1990 which has considerably decreased to 43.9% (184.53 km2) in 2008. There was a rise in total area of plantation crops from 106.27 km2 (25.32%) to 138.20 km2 (32.9%) during this period. Soil and Water Assessment Tool (SWAT) was used to study the effect of LULC on streamflow. SWAT model was calibrated and validated using observed daily streamflow data. The coefficient of correlation (r2) was found to be 0.87 and 0.86 for calibration and validation, respectively. The results found the annual streamflow to increase by 0.77% from 1990 to 2008 whereas the mean monthly streamflow has increased by 9.46% during this period. This was mainly due to the reduction in forest area observed in LULC maps. © 2017, Springer International Publishing Switzerland.
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    Bias correction methods for hydrologic impact studies over India's Western Ghat basins
    (American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2018) Mudbhatkal, A.; Mahesha, M.
    The regional climate models (RCMs) used in the analysis of the impact of climate variables on the hydrology of river basins needs appropriate preprocessing (bias correction) to represent and reproduce future climate with a fair degree of accuracy. The performance of bias corrections methods was assessed in this investigation on the basis of their ability to minimize error on climate variables and streamflow. This work compares the performance of five bias correction methods applied for precipitation and four methods for temperature in modeling the hydrology of the river catchments of theWestern Ghats of India. TheWestern Ghats are a mountainous forest range along the entire west coast of India that plays a major role in the distribution of Indian monsoon rains. Simulations were used to evaluate the performance of the bias correction methods. Using raw RCM, bias corrected precipitation and temperature time series, streamflows were estimated by the soil and water assessment tool (SWAT) hydrological model. The results indicated that the raw RCM-simulated precipitation was biased by 42% and the temperature was biased by 12% across the catchments investigated. Subsequently, a bias of 65% was found in the streamflow. The performance of the delta change correction method was consistently better for precipitation (with Nash-Sutcliffe efficiency, NSE > 0.75 for 5 catchments) and temperature (NSE = 1) compared with other methods. Good performance was observed between the observed and bias corrected streamflow (daily time scale) for the catchments Purna (NSE = 0.97), Ulhas (NSE = 0.64), Aghanashini (NSE = 0.82), Netravathi (NSE = 0.89), and Chaliyar (NSE = 0.90); low performance with an NSE of 0.3 was observed for the catchments Kajvi and Vamanapuram. The methods failed for Malaprabha and Tunga catchments. The results indicate that the delta change correction method performed best in analyzing the hydrological impact of climate variables on the windward side of Western Ghats of India. © 2017 American Society of Civil Engineers.
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    Assessment of variable source area hydrological models in humid tropical watersheds
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Kumar Raju, B.C.K.; Nandagiri, L.
    The objective of this study was to compare the performances of hydrological models that incorporate the Variable Source Area (VSA) mechanism of runoff generation with that of the Soil and Water Assessment Tool (SWAT), which uses the infiltration-excess mechanism. One of the VSA-based model used, SWAT–VSA, has been proposed as a re-conceptualization of the SWAT and uses a topography-based wetness index to identify source areas. In this study, the topography-based wetness index was replaced with a Modified Normalized Difference Water Index (MNDWI) derived from satellite imagery resulting in the SWAT–MNDWI model. Model performances were evaluated through their application in two humid tropical watersheds (Hemavathi–2974 km2; Harangi–538.8 km2) located in the Upper Cauvery River Basin, India. Using relevant data inputs, the three models were applied separately to both watersheds. Models were calibrated for the historical period 2000–2003 and validated for the period 2004–2006 using observed daily observed streamflow records at the watershed outlets. Overall, the SWAT–MNDWI model was the best one in simulating daily streamflow with Nash–Sutcliffe efficiency of 0.85, coefficient of determination of 0.88, percentage bias of 13.2% and root mean square error of 37.48 m3/s for the Hemavathi watershed and corresponding values of 0.88, 0.88, 1.09% and 16.67 m3/s for the Harangi watershed. The spatial patterns of surface runoff generation were similar for the SWAT–VSA and SWAT–MNDWI models, but completely different for the SWAT model. Overall results have demonstrated that models incorporating VSA hydrology, and in particular the proposed SWAT–MNDWI model, provide accurate and convenient tools for distributed hydrologic modelling in humid tropical watersheds. © 2017 International Association for Hydro-Environment Engineering and Research.
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    Assessing climate change impacts on river hydrology – A case study in the Western Ghats of India
    (Springer, 2018) Sharannya, T.M.; Mudbhatkal, A.; Mahesha, M.
    The objective of this study is to evaluate the hydrological impacts of climate change on rainfall, temperature and streamflow in a west flowing river originating in the Western Ghats of India. The long-term trend analysis for 110 yr of meteorological variables (rainfall and temperature) was carried out using the modified Mann–Kendall trend test and the magnitude of the trend was quantified using the Sen’s slope estimator. The Regional Climate Model (RCM), COordinated Regional climate Downscaling EXperiment (CORDEX) simulated daily weather data of baseline (1951–2005) and future RCP 4.5 scenarios (2006–2060) were used to run the hydrological model, Soil and Water Assessment Tool (SWAT), in order to evaluate the effect of climate change on rainfall, temperature and streamflow. Significant changes were observed with regard to rainfall, which have shown decreasing trend at the rate of 2.63 mm per year for the historical and 8.85 mm per year for RCP 4.5 future scenarios. The average temperature was found to be increasing at 0.10?C per decade for both historical and future scenarios. The impact of climate change on the annual streamflow yielded a decreasing trend at the rate of 1.2Mm3 per year and 2.56 Mm 3, respectively for the past and future scenarios. The present work also investigates the capability of SWAT to simulate the groundwater flow. The simulated results are compared with the recession limb of the hydrograph and were found to be reasonably accurate. © 2018, Indian Academy of Sciences.
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    Evaluating the Performance of CHIRPS Satellite Rainfall Data for Streamflow Forecasting
    (Springer Netherlands rbk@louisiana.edu, 2019) Sulugodu, B.; Deka, P.C.
    Streamflow forecasting can offer valuable information for optimal management of water resources, flood mitigation, and drought warning. This research aims in evaluating the effectiveness of CHIRPS satellite rainfall data in comparison with IMD gridded Rainfall Data and development of various flow forecasting models. Daily rainfall data for three decades (1983–2012) over the Nethravathi Basin, Karnataka, India is used for analysis. The analysis is carried out for the monsoon season (June–September), out of which 70% data considered for training the model and remaining for testing. Different input combinations are developed, and soft-computing methods like ANFIS, GRNN, PSO-ANN, and ELM are applied for flow forecasting on a temporal scale. The model performance is evaluated using various statistical indices like NNSE, RRMSE, and MAE. The results indicate that CHIRPS rainfall showed better performance in comparison with IMD data. ELM expressed an enhanced effect when compared to all other methods. The usefulness and effectiveness of CHIRPS data compared to IMD data has been explored. © 2019, Springer Nature B.V.
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    Trend and variability of hydrometeorological variables of Tikur Wuha watershed in Ethiopia
    (Springer, 2020) Ketema, A.; Dwarakish, G.S.
    The study assessed monthly, seasonal, and annual variability and trend of hydrometeorological variables for 1978–2017 of Tikur Wuha watershed in Ethiopia. The Mann-Kendall trend test and Sen’s slope estimator were employed for the trend and size of the trend, respectively. Besides, the coefficient of variation has been computed for variability analysis. The areal average annual rainfall exhibited an insignificant declining trend with a magnitude of 20.8 mm/decade at a watershed scale. The watershed has been suffering from irregular and erratic rainfall during the dry season. Temperature exhibited a statistically significant rising trend with minimum temperature rises faster than that of the maximum temperature. The streamflow of the Tikur Wuha River was found to be increasing at the rate of 21.16 MCM/decade. The increasing trend of streamflow without the corresponding increase of rainfall in the watershed needs further investigation. © 2020, Saudi Society for Geosciences.