Water Analysis Tool Research Articles

Ensemble of artificial intelligence and physically based models for rainfall–runoff modeling in the upper Blue Nile Basin

ABSTRACT This study investigated the performance of the adaptive neuro-fuzzy inference system (ANFIS), feed forward neural network (FFNN), Soil and Water Analysis Tool (SWAT), Hydrologic Engineering Center's Hydraulic Modeling System (HEC-HMS), Hydrologiska Byråns Vattenbalansavdelning (HBV), and support vector regression (SVR) models for rainfall–runoff modeling using gauged and satellite rainfall, and their fusions in the Gilgel Abay watershed, Ethiopia. Afterward, simple average ensemble (SAE), weighted average ensemble (WAE), and neural network ensemble (NNE) techniques were applied to combine the outputs of individual models under three scenarios. The performance of the models was evaluated using Nash–Sutcliffe efficiency (NSE) and root mean square error (RMSE). The results demonstrated that the ANFIS model outperformed all the other single models with validation stage NSE values of 0.864 and 0.875, and RMSE values of 23.58 and 21.84 m3/s for gauge and fusion rainfall data, respectively. Among the physical-based models, SWAT gave better modeling performance with the validation stage NSE values of 0.81 and 0.821 for gauge and fusion rainfall data, respectively. Moreover, an ensemble of artificial intelligence and physical-based models greatly improved the overall modeling performance. The NNE improved the performance of single models up to 15.7 and 21.2 5% for fusion and satellite-based rainfall modeling, respectively.

Alterations in Hydrological Responses under Changing Climate and Land Use/Land Cover across Contrasting Agroecological Environments: A Case Study on the Chemoga Watershed in the Upper Blue Nile Basin, Ethiopia

We analyzed hydrological responses to changing climate and land use/land cover (LULC) for the past (1985–2020) and future (2021–2080) in the Chemoga watershed of the Upper Blue Nile Basin. The watershed comprises four agroecological environments: Moist Kolla, Moist Weyna Dega, Moist Dega, and Wet Wurch. Past and projected LULC changes under business-as-usual (BAU) and land conservation (LC) scenarios were utilized. Climate projections from 2021 to 2080, under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), were downscaled from Global Climate Models. Utilizing the Soil and Water Analysis Tool, we assessed impacts on mean annual surface runoff (SR) and evapotranspiration (ET). Maximum and minimum temperatures increased significantly in the past and future climate scenarios, with a significant rainfall increase observed under SSP5-8.5. Historical trends revealed a 16.6% increase in SR and 7% in ET from 1983–2002 to 2003–2020. Under BAU LULC with the SSP2-4.5 (SSP5-8.5) climate scenario, SR increased by 24% (26.1%) and ET by 3.1% (4.4%) from 2003–2020 to 2021–2050, followed by a subsequent SR rise of 13.7% (14.0%) and ET increase of 6.0% (5.7%) from 2021–2050 to 2051–2080. Conversely, the LC LULC with SSP2-4.5 (SSP5-8.5) resulted in a 5.3% (4.2%) SR decrease and ET increase of 9.7% (11.3%) from 2003–2020 to 2021–2050 and a further SR decrease of 1% (0.7%) and 6.1% (6.9%) ET increase from 2021–2050 to 2051–2080. The Moist Kolla agroecology experienced the highest SR increase due to vegetation clearances for commercial farming. Meanwhile, the LC scenario indicated substantial decreases in SR and marginal increases in ET in the Moist Weyna Dega agroecology due to forest restoration on steep slopes. Overall, SR showed greater sensitivity to LULC changes, while ET was more responsive to climate changes. The results emphasize considering diverse agroecological contexts for effective water resource management under changing climate and LULC scenarios.

Ensemble rainfall–runoff modeling of physically based semi-distributed models using multi-source rainfall data fusion

Abstract This study was aimed at ensemble rainfall–runoff modeling by Soil and Water Analysis Tool (SWAT), the Hydrologic Engineering Center's Hydraulic Modeling System, and Hydrologiska Byråns Vattenbalansavdelning of Gilgel-Abay watershed, Blue Nile basin, Ethiopia. For modeling, daily rainfall datasets of five gauges and three satellites, streamflow, and spatial data were used. In the modeling stage, first, the runoff was simulated separately using the rainfall data of gauges, satellites, and their fusion. Second, ensemble rainfall–runoff simulation of the rainfall dataset fusion-based runoff result was conducted via the proposed weighted average, simple average, and neural network (NNE) ensemble techniques. The results exhibited that all models are good in capturing the rainfall–runoff relationship; however, SWAT showed slight superiority by Nash–Sutcliffe efficiency of 0.807 and 0.821 for gauge and fusion data, respectively. The rainfall fusion ensemble model revealed significant improvement over modeling by satellite rainfall owing to the bias-correcting gauge rainfall over satellite rainfall. The NNE technique enhanced the efficiency of the low-performing satellite-rainfall-based model by 17.5% and the rainfall fusion-based model by 13.3% at the validation stage. In general, the result of this study points out that the rainfall datasets’ fusion from multi-sources would be worthy for the rainfall–runoff simulation of ungauged basins.

Hydrological Modelling in the Ouergha Watershed by Soil and Water Analysis Tool

Hydrological Modelling in the Ouergha Watershed by Soil and Water Analysis Tool

Impacts of combined and separate land cover and climate changes on hydrologic responses of Dhidhessa River basin, Ethiopia

ABSTRACT The combined effects of climate and land cover changes influence hydrologic responses of a basin in an offsetting or synergistic manner depending on the nature and severity of the changes. As such, estimating the impacts of these environmental changes on hydrologic responses is crucial for planning water resources management. However, such a comprehensive study is missing in most basins of Ethiopia, particularly in the Dhidhessa River basin (DRB). The aim of this study is, therefore, to quantify the combined and separate impacts of land cover and climate changes on multiple hydrologic variables for the DRB. The Calibrated Soil and Water Analysis Tool (SWAT) model and statistical techniques were integrated for this study. Quantifying the separate and combined effects of land cover and climate changes on multiple hydrologic responses at a local scale, and determining the relative contribution of the changes are the strength of this study. The result indicated better performance of the SWAT model in simulating water balance components for the DRB. Significant changes in hydrologic responses were observed in response to the land cover changes, and the increasing trends of temperature and rainfall observed during the last 30 years in DRB. The result showed increasing actual evapotranspiration (AET), streamflow, and surface runoff while decreasing groundwater recharge. Surface runoff was more affected by land cover change than by climate change, whereas streamflow and AET were more affected by climate change than land cover change during the last 30 years in the basin. The combined effects of land cover and climate changes played an offsetting effect on groundwater recharge and AET. Overall, the simulated hydrologic responses will have negative effects on water resource availability and agricultural production in the basin and the surroundings. Therefore, implementing integrated watershed management strategies, such as soil and water conservation and afforestation, could minimize the negative impact.

Bharuch District, Gujarat, India: Factor analysis and geographical distribution of water quality characteristics

The goal of this study was to use statistical methods to create baseline data on uranium and associated physicochemical characteristics in the Bharuch district. The district is 6,527 km2 in size and is situated at 21.7051° N, 72.9959° E. Factor analysis is a crucial tool in statistical analytical approaches for obtaining general relationship between measured varaibles. For the study, 144 samples were collected from the Bharuch district of Gujarat during the pre-monsoon (PRMNS) and post-monsoon (POMNS) seasons. A portable multi-parameter water analysis tool was used to test in-situ water quality parameters on-site. In the laboratory, the uranium concentration and the other parameters were examined. Principle component analysis was performed on the data that led to reduction of 18 parameters to 6 during PRMNS and POMNS periods. The eigenvalue-extracted factor generated 86.01 percent and 86.017 percent variation in the PRMNS and POMNS, respectively.

Impact of climate change on streamflow of Melka Wakena catchment, Upper Wabi Shebelle sub-basin, south-eastern Ethiopia

Abstract Climate change is becoming a global concern, dictating the water resource availability of a certain region. This study focuses on the impact of climate change on the streamflow of the Melka Wakena reservoir in the Upper Wabi Shebelle sub-basin using a Soil Water Analysis Tool (SWAT). The climate model variables (precipitation and temperature) are obtained from the Coordinated Regional Downscaling Experiment (CORDEX-Africa) and applied under representative concentration pathway (RCP4.5) and (RCP8.5) scenarios. Bias correction was applied to the climate variables before transferring to the hydrological model (SWAT) to simulate discharge. The performance measures R2, NSE, and Percent Bias (PBIAS) for calibration and validation were 0.69, 0.65, and −5.10 and 0.65, 0.61, and −9.81, respectively. Streamflow was simulated for two consecutive periods from 2021 to 2050 and from 2051 to 2080 for both scenarios and compared with the base period from 1986 to 2015 to explore the impact of climate change on inflows to the reservoir. The result obtained showed that the precipitation was predicted to be mildly decreasing, whereas overall annual flow was projected to be insignificantly decreasing under RCP4.5 and RCP8.5 scenarios. The impact of climate change on the water resource of the study area was predicted to be a statistically insignificant reduction.

Modeling Surface Water Availability for Irrigation Development in Mbarali River Sub-Catchment Mbeya, Tanzania

Although Tanzania has a large land suitable for irrigation development, only 4.2% of the arable land which is potential for irrigation has been developed. Mbarali District is characterized by commercial and small-scale irrigation activities for paddy production. Currently, surface water availability for irrigation in Mbarali District is dwindling due to high water demands. Inadequate studies that estimate water availability for irrigation is one of the underlying factors to the lack of irrigation development in many parts of Tanzania including in Mbarali District. This study, therefore, aimed to model surface water availability for irrigation development in Mbarali River sub-catchment Mbeya, Tanzania. The Soil and Water Analysis Tool (SWAT) model and field observations were used to accomplish the study. The model estimates that Mbarali River sub-catchment receives about 631 mm of total mean precipitation annually. About 53% of received precipitation is lost through evapotranspiration, 12% recharged to deep aquifer and the remaining 35% discharged to the stream flow through surface runoff, lateral flow and return flow from unconfined aquifer. Discharge to the steam flow contributes to the total annual means of river discharge ranging from 0 - 10 cubic meters per second at upper catchment to 120 - 140 cubic meters per second at lower catchment. The study recommends that the lower reach of the Mbarali River sub-catchment is potential for irrigation than the upper reach as it has potential river flow that can support irrigation activities. The study also notes the urgent need for water reallocation plan to meet competing water needs in the lower reach of Mbarali River sub-catchment. Moreover, the study addresses the potentiality of irrigation in upper catchment under sustainable water management practices including excavation of small ponds to capture and store surface runoff for dry season use or to supplement irrigation as the rainfall declines.

Evaluating the potential impact of climate change on the hydrology ofRibbcatchment, Lake Tana Basin, Ethiopia

AbstractScientific findings indicated there is climate change that affects given hydrology and, hence, water availability worldwide. To quantify its impact on a specific catchment scale, since spatial and temporal variability of climate change impact, this study was carried out at Ribb catchment, Lake Tana basin, Ethiopia. The catchment hydrology was represented by the Soil and Water Analysis Tool (SWAT) through using historical observed data. Regional Climate Model (RCM) projection data set for Nile Basin studies at Representative Concentration Pathway (RCPs) (RCP4.5 and RCP8.5) were used for future streamflow generation on three-time horizons; 2020s (2011–2040), 2050s (2041–2070), and 2080s (2071–2098). A baseline period (1976–2005) was used as a reference. SWAT was calibrated (R2 = 0.83 and NSE = 0.74) and validated (R2 = 0.72 and NSE = 0.71). The analysis was done based on the changes from the baseline period to the 2080s. Temperature showed an increasing trend but rainfall is decreasing. The mean annual streamflow could potentially reduce from 42.78 m3/s to 40.24 m3/s and from 42.78 m3/s to 37.58 m3/s based on RCP4.5 and RCP8.5 scenarios, respectively. On a monthly time scale, decreases in streamflow were found from March to August whereas there was a slight increase from September to February. Concerning individual months, June flows were found to have maximum impact in both scenarios (63.3% at RCP8.5 and 55.45% at RCP4.5 scenarios). The least impacted month was August based on the RCP8.5 scenario which is decreased by 6.64% and April based on the RCP4.5 scenario which is reduced by 1.21%. Looking at total volume, July showed a maximum decrease in both scenarios which is reduced by 21.08 m3/s at the RCP4.5 scenario and 51.22 m3/s at the RCP8.5 scenario. The maximum increase was found in October with 10.31 m3/s and 11.26 m3/s at RCP4.5 and RCP8.5 scenarios respectively. The future streamflow of Ribb River has decreased annually and monthly due to increasing temperature and reduction of rainfall.

Effect on sediment delivery ratio by changes in land use land cover and construction of hydraulic structures at sub basin scale

Many areas of the world are particularly vulnerable to sedimentation. Determining the amount of soil erosion and sediment rate from watersheds would be the first step in reducing sedimentation. Soil and Water Analysis Tool (SWAT) based on Geographic Information System (GIS) was used to determine sediment yield and Sediment Delivery Ratio (SDR). This paper’s main objective is to assess the impact of land-use change on SDR at the sub-basin scale. Land-use changes indicated a vast reduction of 19% in the forest area, which causes an increase in agricultural land and commercial land. Therefore, SDR must be increased, but the study area’s average SDR trend is decreasing from 1985 to 2015. But, sub-basin-scale, sub-basins no. 17, 18, and 24 are decreasing from 1985 to 2005 and increasing from 2005 to 2015.

Impact of post- reclamation of soil by large-scale, small-scale and illegal mining on water balance components and sediment yield: Pra River Basin case study

Gold mining is extremely valuable for countries involved in it due to the potential for employment, income allocation and socio-economic development. As a result of the attraction of international investors by governments of countries rich in this natural resource and increasing gold prices, large-scale, small-scale and unlicensed and illegal (Galamsey) mining activities are expanding. This expansion can have significant effects on the environment, such as pollution and altering the hydrological regime, constituting a threat to the natural ecosystems and the health of the populace staying in gold mining zones. This research focuses on the evaluation of the effects of different types of soil reclamation measures used by large-scale, small-scale and galamsey miners on hydrological components and sediment yield in the Pra River Basin (PRB), Ghana, using the Soil and Water Analysis Tool (SWAT). Soil samples were collected from the reclaimed sites of the three mining types, analyzed and used as input into the SWAT model to assess their effect on the hydrological components and sediment yield. The results showed that apart from the first two soil layers of large scale, almost all the three mining types have a significant change in the reclaimed soil constituents of various layers of the soil. The trend and magnitude of post-reclamation impact on hydrological components from galamsey and small-scale mining are almost the same. With reference to the natural background, galamsey and small-scale activity, respectively, increased surface runoff by 51.5 % and 43.9 %, and reduced baseflow by 24.4 % and 22.9 %, while large-scale activity depicted the decrease in runoff and increase in baseflow. Sediment yield from all the three types of gold mining increased significantly. In the PRB, galamsey prominently produced much sediment (161.9 ton/year), followed by small-scale (151.1 ton/year) and large-scale (67.5 ton/year). This paper identified that the effects of land degradation linked to mining cannot be attributed only to galamsey but also to small-scale and large-scale mining. From the outcomes, special attention should be given to reclamation and water management activities that can solve emerging regulatory and environmental management problems that are being encountered by the mining sector.

Performance evaluation of multiple satellite rainfall products for Dhidhessa River Basin (DRB), Ethiopia

Abstract. Precipitation is a crucial driver of hydrological processes. Ironically, a reliable characterization of its spatiotemporal variability is challenging. Ground-based rainfall measurement using rain gauges is more accurate. However, installing a dense gauging network to capture rainfall variability can be impractical. Satellite-based rainfall estimates (SREs) could be good alternatives, especially for data-scarce basins like in Ethiopia. However, SRE rainfall is plagued with uncertainties arising from many sources. The objective of this study was to evaluate the performance of the latest versions of several SRE products (i.e., CHIRPS2, IMERG6, TAMSAT3 and 3B42/3) for the Dhidhessa River Basin (DRB). Both statistical and hydrological modeling approaches were used for the performance evaluation. The Soil and Water Analysis Tool (SWAT) was used for hydrological simulations. The results showed that whereas all four SRE products are promising to estimate and detect rainfall for the DRB, the CHIRPS2 dataset performed the best at annual, seasonal and monthly timescales. The hydrological simulation-based evaluation showed that SWAT's calibration results are sensitive to the rainfall dataset. The hydrological response of the basin is found to be dominated by the subsurface processes, primarily by the groundwater flux. Overall, the study showed that both CHIRPS2 and IMERG6 products could be reliable rainfall data sources for the hydrological analysis of the DRB. Moreover, the climatic season in the DRB influences rainfall and streamflow estimation. Such information is important for rainfall estimation algorithm developers.

Climate change impact on streamflow in a tropical basin of Ghana, West Africa

Study regionPra River Basin, Ghana, West Africa. Study focusIn this study, variations of the future streamflow in the Pra River Basin (PRB), are projected using the Soil and Water Analysis Tool (SWAT) model with bias-corrected climate data from regional climate models (RCMs) for the near 21 st century (2010–2039), the mid 21 st century (2040–2069), and the end of the 21 st century (2070–2099), under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Weighting, scaling and ranking techniques were applied to the data from each of the seventeen climate stations to select the climate models that best reproduced the observation dataset. New hydrological insights for the regionThe results from the calibration and validation (R2 and NSE > 0.75, and PBIAS within ±10 %), revealed good simulation of the PRB hydrology from the SWAT model. Annually, streamflow in the near and the mid-21st century is projected to increase within 4 % and 12 % while a reduction was projected at the end of the 21 st century with the RCP4.5 emission scenario. The simulation results from the RCP8.5 scenario showed increase streamflow throughout the 21 st century applying the best performing models. Monthly streamflow variations varied between -15 % and 23 % for RCP4.5, and -24 % to 24 % for RCP8.5. Generally, increasing streamflow was highest in the RCP4.5 emission scenario. In view of the model outcomes, the PRB is expected to experience upsurge in streamflow by the near and the mid of the 21 st century. This would require proper planning by applying cost-effective adaptative water management strategies to provide for the probable influence of climate change on the future water resources of the basin.

Estimating wind power generation capacity in Zimbabwe using vertical wind profile extrapolation techniques: A case study

Only 40% of Zimbabwe’s population has access to electricity. The greater proportion of the power is generated from thermal stations, with some from hydro and solar energy sources. However, there is little investment in the use of wind for electricity generation except for small installations in the Eastern Highlands, as Zimbabwe generally has wind speeds which are too low to be utilised for electricity generation. This paper presents the use of vertical wind profile extrapolation methods to determine the potential of generating electricity from wind at different hub heights in Zimbabwe, using the Hellman and exponential laws to estimate wind speeds. The estimated wind speeds are used to determine the potential of generating electricity from wind. Mangwe district in Matabeleland South province of Zimbabwe was used as a test site. Online weather datasets were used to estimate the wind speeds. The investigation shows that a 2.5kW wind turbine installation in Mangwe can generate more than 3MWh of energy per annum at hub heights above 40m, which is enough to supply power to a typical Zimbabwean rural village. This result will encourage investment in the use of wind to generate electricity in Zimbabwe.
 Highlights
 
 Wind power utilisation is low in Zimbabwe.
 Vertical wind profile is estimated using extrapolation methods.
 Online weather data for soil and water analysis tool was used.
 Electricity can viably be generated from wind in Zimbabwe.

Hydrological modeling in the Upper Blue Nile basin using soil and water analysis tool (SWAT)

Hydrological models are essential to understand the hydrological response of the basin. It is one of the most significant aspects of water resources management and development programs at the small catchment or basin level. A semi-distributed, physical-based hydrologic modeling system, SWAT, was used to model the hydrological responses of the Upper Blue Nile basin. The model was calibrated and validated using the sequential uncertainty fitting (SUFI-2) algorithm in SWAT-CUP. The coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE), and percent of bias (PBIAS) were used to measure the performance of the model. The value of R2, NSE, PBIAS was range from 0.81–0.85, 0.68–0.83 and − 10.8 to (− 4.7%) during calibration and 0.89–0.93, 0.88–0.89 and 8.3–9.7% during validation period, respectively. The results indicated a strong correlation between the observed and simulated streamflow during the calibration and validation periods. The overall hydrological water balance analysis showed that 49.5% of precipitation is lost by evapotranspiration, while 22.43% of precipitation is contributed to streamflow as surface flow. Furthermore, the hydrological water balance components of the basin showed a good spatial correlation. Since the water resource planning and management need the temporal and spatial water resource information, the results of this study will be used as a guide for the proposed water resource development projects of the basin.

Development of framework for assessment of impact of climate change in a command of water resource project

A framework comprising of four interdependent modules has been developed to analyse demand–supply scenarios under future uncertainties of climate change in an irrigation command where any mismatch can affect sustainability and wellbeing of the rural population. In the absence of runoff records, the water balance module of framework computes daily runoff from catchment considering all inputs, outputs and losses from the system. The climatic parameters and rainfall were forecasted for three future projected periods using statistical downscaling for six different climate projections. The Soil and Water Analysis Tool (SWAT), a physically based spatially distributed hydrological model and SWAT-CUP, an application for calibration and uncertainty analysis of SWAT model have been used to calibrate and validate a model for the base period (BP:1981–2015) and further applied to generate multiple future runoff series to asses water availability. The module-IV was designed to compute evapotranspiration using ETo calculator (a software to compute evapotranspiration) and then irrigation demand for Tandula command in the Chhattisgarh state of India considering present overall efficiency of 51% for the base (1991–2015) and future assessment periods. The analysis of all projected scenarios suggested an increase of annual temperature from present 26.2°–27.1°, 27.3° and 27.8°C during near (FP-1: 2020–2035), mid (FP-2: 2046–2064) and far century (FP-3: 2081–2099) periods, respectively, may demand more water which could be adversely affected by reduced rainfall. The water requirement may vary in the range of 410.4–464 MCM and supply from 426.2 to 453.2 MCM based on future projection from GCMs.

Assessment of land use impact on hydrological response using Soil and Water Analysis Tool (SWAT) in Babak watershed, Lombok Island, Indonesia

Assessment of land use impact on hydrological response using Soil and Water Analysis Tool (SWAT) in Babak watershed, Lombok Island, Indonesia

Methods for integrating high-resolution land, climate, and infrastructure scenarios in a hydrologic simulation model

Global alterations of the hydrologic cycle by humans have led to alarming rates of water shortages and irreversible ecosystem change. Our ability to manage water resources lies in accurately modeling water availability at scales meaningful to management. Although hydrologic models have been used to understand the implications of future climate and land cover change on regional water availability, many modeling approaches fail to integrate human infrastructures (HI) with bio-geophysical drivers to facilitate sustainable regional water resource management. This paper presents an integrated framework, inclusive of modeling and data needs, to quantify the effects of both bio-geophysical and HI influence on regional surface water hydrology. The framework enables the integration of high spatial and temporal anthropogenic alterations of water availability for identifying hot-spots and hot-moments of hydrological stresses within individual river-segments using a hydrologic simulation model, Soil and Water Analysis Tool (SWAT).•A high-resolution river network for the study region with a greater spatial granularity compared to contemporary SWAT applications attempted to account for HI.•The anthropogenic influence on water balance for each river segment was estimated using data on human infrastructures, such as water intakes, power production facilities, discharges, dams, and land transformation.

Towards the use of conceptual models for water resource assessment in Indian tropical watersheds under monsoon-driven climatic conditions

Water resource assessment is important for integrated water resources management of a basin to which rainfall is a vital component. Generally, semi-distributed to distributed models are used for water resource management studies. Higher data requirement and simulation time restrict the use of these models. Lumped conceptual models are drawing attention these days owing to their simplicity and minimum data requirement. In the present study, the performance of conceptual models Genie Rural a 4 parametres Journalie (GR4J) and Australian Water Balance Model (AWBM) was evaluated in comparison with semi-distributed Soil and Water Analysis Tool (SWAT) model. The selected study area, Upper Godavari River Basin, is in the windward side of Western Ghats in India, which receives heavy rainfall during south-west monsoon season. However, this region faces water scarcity issues in non-monsoon period due to lack of proper water management scenarios. Five catchments in upper Godavari basin are used for the analysis. Spatiotemporal analysis of rainfall is done to understand its effect on streamflow at the catchment outlet. The efficacy of model predictions has been analysed statistically in terms of Nash–Sutcliffe Efficiency, coefficient of determination (R2) and percentage bias. Flow duration curves and time series diagram of streamflow predictions are also compared to better understand the results. All three models predicted streamflow with reasonable accuracy. Considering structural simplicity, less data requirement and simplicity in calibration process, this study proposes conceptual models over SWAT in the regions facing data scarcity.

Prediction of soil and water conservation structure impacts on runoff and erosion processes using SWAT model in the northern Ethiopian highlands

PurposeLand degradation due to soil erosion is a serious threat to the highlands of Ethiopia. Various soil and water conservation (SWC) strategies have been in use to tackle soil erosion. However, the effectiveness of SWC measures on runoff dynamics and sediment load in terms of their medium- and short-term effects has not been sufficiently studied.Materials and methodsA study was conducted in 2011 to 2015 in the Gumara-Maksegnit watershed to study the impacts of SWC structures on runoff and soil erosion processes using the soil and water analysis tool (SWAT) model. The study was conducted in two adjacent watersheds where in one of the watersheds, SWC structures were constructed (treated watershed (TW)) in 2011, while the other watershed was a reference watershed without SWC structures (untreated watershed (UW)). For both watersheds, separate SWAT and SWAT-CUP (SWAT calibration and uncertainty procedure) projects were set up for daily runoff and sediment yield. The SWAT-CUP program was applied to optimize the parameters of the SWAT using daily observed runoff and sediment yield data.Results and discussionThe runoff simulations indicated that SWAT can reproduce the hydrological regime for both watersheds. The daily runoff calibration (2011–2013) results for the TW and UW showed good correlation between the predicted and the observed data (R2 = 0.78 for the TW and R2 = 0.77 for the UW). The validation (2014–2015) results also showed good correlation with R2 values of 0.72 and 0.70 for the TW and UW, respectively. However, sediment yield calibration and validation results showed modest correlation between the predicted and observed sediment yields with R2 values of 0.65 and 0.69 for the TW and UW for the calibration and R2 values of 0.55 and 0.65 for the TW and UW for the validation, respectively.ConclusionsThe model results indicated that SWC structures considerably reduced soil loss by as much as 25–38% in the TW. The study demonstrated that SWAT performed well for both watersheds and can be a potential instrument for upscaling and assessing the impact of SWC structures on sediment loads in the highlands of Ethiopia.