scholarly journals Calibration of a modelling approach for sediment yield in a wattle plantation, KwaZulu-Natal, South Africa

Water SA ◽  
2020 ◽  
Vol 46 (2 April) ◽  
Author(s):  
BC Scott-Shaw ◽  
TR Hill ◽  
JS Gillham
Keyword(s):  
South Africa ◽  
Assessment Tool ◽  
Swat Model ◽  
Catchment Scale ◽  
Vegetation Growth ◽  
Erosion Risk ◽  
Kwazulu Natal ◽  
Input Parameters ◽  
Risk Areas ◽  
Managed Ecosystems

Hydrological modelling is an appropriate approach to investigate the effect of interactions of climate, land-use and soil on the water-use of natural or managed ecosystems, in particular where spatial heterogeneity exists. The Soil and Water Assessment Tool (SWAT) model has evolved into one of the most widely used catchment-scale hydrological models, which has been extensively used to better understand hydrological processes. In this paper, the SWAT model was adopted to simulate a wattle plantation in KwaZulu-Natal, South Africa. User-defined vegetation growth, soil and management input parameters were constructed for the study area based on site measurements. These parameters were subsequently modified using the Sequential Uncertainty Fitting (SUFI-2) analysis routine to calibrate the model. The calibrated model captured seasonal trends in the observed sediment and streamflow data. The compilation of spatially explicit sediment output provides a useful approach to manage catchments by identifying high erosion-risk areas. The SWAT model, using site-specific input parameters, provides a platform for subsequent hydrological and sediment modelling in South Africa.

scholarly journals Improved SWAT vegetation growth module for tropical ecosystem

2017 ◽  
Author(s):  
Tadesse Alemayehu ◽  
Ann van Griensven ◽  
Willy Bauwens
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Soil Moisture ◽  
Management Practices ◽  
Assessment Tool ◽  
Swat Model ◽  
Evergreen Forest ◽  
Tropical Ecosystem ◽  
Area Index ◽  
Vegetation Growth

Abstract. The Soil and Water Assessment Tool (SWAT) is a globally applied river basin eco-hydrological simulator in a wide spectrum of studies, ranging from land use change and climate change impacts studies to research for the development of best water management practices. However, SWAT has limitations in simulating the seasonal growth cycles for trees and perennial vegetation in tropics, where the major plant growth controlling factor is the rainfall (via soil moisture) rather than temperature. Our goal is to improve the vegetation growth module of the SWAT model for simulating the vegetation parameters such as the leaf area index (LAI) for tropics. Therefore, we present a modified SWAT version for the tropics (SWAT-T) that uses of a simple but robust soil moisture index (SMI) – a quotient of the rainfall (P) and reference evapotranspiration (PET) – to initiate a new growing season after a defined dry season. Our results for the Mara Basin (Kenya/Tanzania) show that the SWAT-T simulated LAI corresponds well with the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI for evergreen forest, savanna grassland and shrubs, indicating that the SMI is a reliable proxy to dynamically initiate a new growing cycle. The water balance components (evapotranspiration and flow) simulated by the SWAT-T exhibit a good agreement with remote sensing-based evapotranspiration (RS-ET) and observed flow. The SWAT-T simulator with the proposed improved vegetation growth module for tropical ecosystem could be a robust tool for several applications including land use and climate change impact studies.

scholarly journals Combined use of volume-area and volume-length scaling relationships in glacio-hydrological simulation

2018 ◽  
Vol 49 (6) ◽  
pp. 1753-1772 ◽  
Author(s):  
Xiaolei Wang ◽  
Yiqing Zhang ◽  
Yi Luo ◽  
Lin Sun ◽  
Muhammad Shafeeque
Keyword(s):  
Assessment Tool ◽  
Swat Model ◽  
Glacier Area ◽  
Catchment Scale ◽  
Equilibrium Line Altitude ◽  
Hydrological Simulation ◽  
Glacier Terminus ◽  
Glacier Melt ◽  
Length Scaling ◽  
Hydrological Station

Abstract Glacier changes are driven by glacier melt, which in turn affects streamflow. This paper describes an accounting scheme for glacier area change distribution across elevation profiles for application in the glacier module of the Soil and Water Assessment Tool (SWAT) model. In addition to volume-area scaling relationship in the module, the paper introduced volume-length scaling relations to estimate changing glacier terminus and update glacier area changes between equilibrium line altitude (ELA) and the terminus. The improved scheme was used in the nested Urumqi Glacier No. 1 catchment and Urumqi River Basin in Tienshan Mountains, China. Comparison of the simulated and observed data suggested that the new scheme accurately reproduced the length and area changes of Glacier No. 1. The contributions of glacier melt and ice melt to runoff were estimated at 71% and 38% for Glacier No. 1 Hydrological Station and 11.1% and 5.8% for Yingxiongqiao Hydrological Station, respectively. This helped to better interpret long-term monitored glacio-hydrological processes of Glacier No. 1 and the variation of glacier melt contribution to streamflow at the catchment scale.

scholarly journals Study on the Relationship between Snowmelt Runoff for Different Latitudes and Vegetation Growth Based on an Improved SWAT Model in Xinjiang, China

2021 ◽  
Vol 13 (3) ◽  
pp. 1189
Author(s):  
Yongchao Duan ◽  
Min Luo ◽  
Xiufeng Guo ◽  
Peng Cai ◽  
Fu Li
Keyword(s):  
High Altitude ◽  
Assessment Tool ◽  
Swat Model ◽  
Precipitation Pattern ◽  
Mountainous Area ◽  
Snowmelt Runoff ◽  
Mountainous Areas ◽  
Snow Melting ◽  
Modified Model ◽  
Vegetation Growth

Rivers located in high altitude mountainous areas provide a large number of water resources and are also high-risk areas for seasonal snow melt floods. The accurate calculation and simulation of snow melting processes can provide reliable data for flood disaster prediction. In order to make the Soil and Water Assessment Tool (SWAT) model more suitable for high altitude mountainous areas, the effect of the daily accumulated temperature on the precipitation pattern and snow melting is fully considered. Applying the modified model to three mountain systems with different latitudes in Xinjiang can not only improve our understanding of the characteristics of snowmelt flooding but can also be used to test the applicability of the modified model. Through comparison, it was found that the simulation accuracy of the modified model of the flood peak value was improved by 56.19%. The correlation coefficient between the Normalized Difference Vegetation Index (NDVI) and snowmelt increased from 0.27 to 0.68. This study provides a new method for accurately understanding the process of snowmelt runoff in the mountainous area and provides new insights into the effects of snowmelt runoff on vegetation growth at different latitudes.

scholarly journals Evaluating the SWAT model to predict streamflow, nitrate loadings and crop yields in a small agricultural catchment

2019 ◽  
Vol 48 ◽  
pp. 1-9 ◽  
Author(s):  
Andreas Bauwe ◽  
Petra Kahle ◽  
Bernd Lennartz
Keyword(s):  
Nitrogen Fertilization ◽  
Assessment Tool ◽  
Crop Yields ◽  
Swat Model ◽  
Experimental Studies ◽  
Validation Period ◽  
Catchment Scale ◽  
Daily Data ◽  
High Level ◽  
Northeastern Germany

Abstract. This study aimed to evaluate the applicability of the Soil and Water Assessment Tool (SWAT) to predict streamflow, nitrate loadings and crop yields for a small agricultural catchment in northeastern Germany. To this end, a 167 ha catchment was delineated consisting of 10 hydrological response units. Daily data for streamflow and nitrate loadings from 2004 to 2015 were used to calibrate and validate the model, while annual values for crop yields (winter wheat, winter barley, rapeseed, maize silage) were available. In addition, the detailed field maps provided by the local farmer were used to implement exact crop rotations and nitrogen fertilization into the model. Nash-Sutcliffe-Efficiencies for streamflow were 0.54 during the calibration and 0.57 for the validation period. The modeling performance for nitrate loadings were lower with 0.31 for the calibration and 0.42 for the validation period. The average crop yields were reproduced well, while SWAT failed to reproduce the inter-annual crop yield variations. A scenario analysis revealed that a slight decrease of nitrogen fertilization leads to significant reductions in nitrate loadings, while crop yields remained on a high level. The outcome of the study may help practitioners to operate according to an economic and environmental optimal N management. Nevertheless, experimental studies with varying fertilization intensities at catchment scale are needed to underpin the modeling results.

scholarly journals A Catchment Scale Assessment of Water Balance Components: A Case Study of Chittar Catchment in South India

2021 ◽  
Author(s):  
Dinagarapandi Pandi ◽  
Saravanan Kothandaraman ◽  
K S Kasiviswanathan ◽  
Mohan Kuppusamy
Keyword(s):  
Water Balance ◽  
Assessment Tool ◽  
Moving Average ◽  
Swat Model ◽  
Meteorological Variables ◽  
Coefficient Of Determination ◽  
Time Interval ◽  
Catchment Scale ◽  
Water Balance Components ◽  
Management And Development

Abstract Analyzing the Water Balance Components (WBCs) of catchment help in assessing the water resources for their sustainable management and development. This paper used Soil and Water Assessment Tool (SWAT) model mainly to analyze the variation in the WBCs through the change in the Land Use and Land Cover (LULC) and meteorological variables. For this purpose, the model used the inputs of LULC and meteorological variables between the year 2001-2020 at five year and daily time interval respectively from the Chittar river catchment. The developed models were evaluated using SWAT-CUP split-up procedure (pre-calibration and post-calibration). The model was found to be good in calibration and validation, yielding the coefficient of determination (R2) of 0.94 and 0.81 respectively. Furthermore, WBCs of the catchment were estimated for the near future (2021 - 2030) at monthly and annual scale. For this endeavour, LULC was forecasted for the year 2021 and 2026 using Celluar Automata (CA)-ANN and for the same period meteorological variables were also forecasted using the smoothing moving average method from the historical data.

scholarly journals Climate change impact assessment on water security in South Africa: A case study in a semi-arid river basin

2019 ◽  
Vol 98 ◽  
pp. 06014
Author(s):  
Yali Woyessa
Keyword(s):  
Climate Change ◽  
South Africa ◽  
River Basin ◽  
Historical Data ◽  
Assessment Tool ◽  
Greenhouse Gas Emission ◽  
Swat Model ◽  
Climate Change Scenarios ◽  
The Impact ◽  
Semi Arid

The main aim of this paper is to assess the impact of regional climate change scenarios on the availability of water resources in a semi-arid river basin in South Africa using a hydrological model called Soil and Water Assessment Tool (SWAT). In this paper, climate change data was derived from two downscaling approaches, namely statistical downscaling experiment (SDE) and dynamic downscaling (CORDEX). These were derived from the GCM simulations of the Coupled Model Inter-comparison Project Phase-5 (CMIP5) and across two greenhouse gas emission scenarios known as Representative Concentration Pathways (RCP) 4.5 and 8.5. The spatial resolution of the dataset for the SDE method is 25 km × 25 km and 50 km × 50 km for the CORDEX method. Six GCM models were used for SDE set of data and four for the CORDEX set of data. SWAT model was run using these data for a period of up to mid-century (2020 – 2050) for SDE and for a period of up to the end of this century (2020 – 2100) for CORDEX data. The results were then compared with long-term historical data (1975-2005). Comparison of measured data with simulated historical data showed strong correlation (R2 = 0.95 for SDE data and R2 = 0.92 for CORDEX data), which is indicative of the reliability of projected future climate.

scholarly journals Soil Erosion Modelling and Risk Assessment in Data Scarce Rift Valley Lake Regions, Ethiopia

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1684 ◽  
Author(s):  
Alemu Aga ◽  
Bayou Chane ◽  
Assefa Melesse
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Assessment Tool ◽  
Swat Model ◽  
Slope Length ◽  
Erosion Risk ◽  
Management Plans ◽  
Erosion Modelling ◽  
Lakes And Reservoirs ◽  
Bathymetric Changes

To prolong the useful life of lakes and reservoirs, prioritizing watersheds by severity and risk of soil erosion is an essential index to develop sound sediment management plans. This study aims to predict soil erosion risk and sediment yield using Soil and Water Assessment Tool (SWAT) model in Lake Ziway basin, Ethiopia, and the model result is validated with lake bathymetric changes. The SUFI-2 program was applied for a model calibration and the performance of the model was assessed. The catchment prioritization study indicated that some sub-basins having the same soil type and land use but a higher slope gives higher sediment yield. This confirms that, in the basin, the upland is the main source of sediment for the lake, hence the variation of sediment yield is more sensitive to terrain slope. Furthermore, the soil conservation scenarios demonstrated in SWAT that reduce the slope length of the watershed by 50% for a slope greater than 5% are decreasing the sediment yield of the basin by 55%. The bathymetric differencing of the lake indicates that the sediment was accumulating at a rate of 3.13 t/ha/year while a calibrated SWAT model resulted in 5.85 t/ha/year. The identified reasons for these variations are the existence of outlet for the lake, floodplain depositions and abstraction of sediment (sand mining) from the tributary rivers before flowing to the lake.

scholarly journals Assessing the Impact of Man–Made Ponds on Soil Erosion and Sediment Transport in Limnological Basins

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2526
Author(s):  
Mario J. Al Sayah ◽  
Rachid Nedjai ◽  
Konstantinos Kaffas ◽  
Chadi Abdallah ◽  
Michel Khouri
Keyword(s):  
Sediment Transport ◽  
Soil Erosion ◽  
Assessment Tool ◽  
Swat Model ◽  
Erosion Risk ◽  
Sediment Yields ◽  
Risk Zones ◽  
Transport Patterns ◽  
Scientific Attention ◽  
The Impact

The impact of ponds on basins has recently started to receive its well-deserved scientific attention. In this study, pond-induced impacts on soil erosion and sediment transport were investigated at the scale of the French Claise basin. In order to determine erosion and sediment transport patterns of the Claise, the Coordination of Information on the Environment (CORINE) erosion and Soil and Water Assessment Tool (SWAT) models were used. The impact of ponds on the studied processes was revealed by means of land cover change scenarios, using ponded versus pondless inputs. Results show that under current conditions (pond presence), 12.48% of the basin corresponds to no-erosion risk zones (attributed to the dense pond network), while 65.66% corresponds to low-erosion risk, 21.68% to moderate-erosion risk, and only 0.18% to high-erosion risk zones. The SWAT model revealed that ponded sub-basins correspond to low sediment yields areas, in contrast to the pondless sub-basins, which yield appreciably higher erosion rates. Under the alternative pondless scenario, erosion risks shifted to 1.12%, 0.52%, 76.8%, and 21.56% for no, low, moderate, and high-erosion risks, respectively, while the sediment transport pattern completely shifted to higher sediment yield zones. This approach solidifies ponds as powerful human-induced modifications to hydro/sedimentary processes.

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