Spatiotemporal Analysis of the Hydrological Responses to Land-Use Land-Cover Changes in the Manafwa Catchment, Eastern Uganda

Abstract

This study evaluated the impact of land-use land-cover (LULC) change (LULCC) on the hydrologic processes of the Manafwa Basin in eastern Uganda using the Soil and Water Assessment Tool (SWAT) model. Model inputs included the 1995, 2008, and 2017 LULC maps; digital elevation model; and soil, climatological, and hydrologic data. The Calibration and Uncertainty Program Sequential Uncertainty Fitting algorithm was used to calibrate and validate the SWAT model. The model was validated for 2011 to 2013 using daily river discharge. Model statistical measures obtained during calibration and validation ranged from 0.79 to 0.94 for coefficient of determination, from 0.65 to 0.79 for Nash–Sutcliffe coefficient and between −12.0 and − 30.2 for percentage bias. Spatial coverage of commercial farmland and built-up areas increased by 405 percent and 337 percent, respectively, while wetland and tropical high forests decreased 82 percent and 41 percent, respectively, during the period from 1995 to 2017. There is increased annual surface runoff (67 percent), sediment yield (109 percent), and water yield (72 percent) and decreased potential evapotranspiration (32 percent) and actual evapotranspiration (31 percent). Therefore, implementation of integrated basin management strategies such as soil and water conservation and afforestation could reverse the negative impacts and ensure effective water resources management.

本研究使用SWAT模型评估了土地利用和土地覆盖变化(LULC)对乌干达东部Manafwa盆地水文过程的影响。模型输入包括: 1995年、2008年和2017年的LULC地图、数字高程模型, 以及土壤、气候和水文数据。采用校正和不确定程序序列不确定性拟合算法(Calibration and Uncertainty Program Sequential Uncertainty Fitting), 对SWAT模型进行了校正和验证。利用每日流量数据, 对2011年至2013年的模型进行了验证。模型校正和验证的测定系数为0.79至0.94, 纳什-萨克利夫系数为0.65至0.79, 百分比偏差为−12.0至−30.2。1995年至2017年, 商业农田和建成区的空间覆盖率分别增长了405%和337%, 湿地和热带高林的空间覆盖度分别减少了82%和41%。年地表径流、沉积量和产水量分别增加了67%、109%和72%, 潜在和实际蒸散量分别降低了32%和31%。因此, 实施水土保持和植树造林等流域综合管理策略, 可能会扭转负面影响、确保有效的水资源管理。

En este estudio se evaluó el impacto de los cambios en el uso del suelo y en la cubierta del suelo (LULC) sobre los procesos hidrológicos de la Cuenca del Manafwa, en Uganda oriental, usando el modelo de la Herramienta de Evaluación del Suelo y el Agua (SWAT). Los inputs del modelo incluyeron los mapas LULC de 1995, 2008 y 2017; el modelo de elevación digital; y datos pedológicos, climatológicos e hidrológicos. Para calibrar y validar el modelo SWAT se usó el algoritmo de Ajuste de Incertidumbre Secuencial del Programa de Calibración e Incertidumbre. El modelo se validó para el período de 2011 a 2013 usando la descarga diaria del río. Las medidas estadísticas del modelo, que se obtuvieron durante la calibración y la validación, variaron de 0,79 a 0,94 para el coeficiente de determinación , de 0,65 a 0,79 para el coeficiente Nash-Sutcliffe y entre –12,0 y –30,2 para el sesgo porcentual. Las cuberturas espaciales de los terrenos agrícolas comerciales y de las áreas edificadas se incrementaron en un 405 por ciento y 337 por ciento, respectivamente, mientras que los humedales y las altas selvas tropicales decrecieron en un 82 por ciento y un 41 por ciento, respectivamente, durante el período que se extiende de 1995 a 2017. Se registra un aumento de la escorrentía superficial anual (67 por ciento), la carga de sedimentos (109 por ciento) y el rendimiento hídrico (72 por ciento), y una disminución de la evapotranspiración potencial (31 por ciento). Por lo tanto, la implementación de estrategias de manejo integrado de cuencas, tales como la conservación de suelos y aguas, y la reforestación, podrían revertir los impactos negativos y asegurar un manejo efectivo de los recursos hídricos.

Key Words:

• hydrological processes
• LULC
• Manafwa River
• SWAT
• Uganda
• water resources

关键词:

• 水文过程
• LULC
• Manafwa河
• SWAT
• 乌干达
• 水资源

Palabras clave:

• LULC
• procesos hidrológicos
• recursos hídricos
• rio Manafwa
• SWAT
• Uganda

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Correction

Disclosure Statement

No potential conflict of interest was reported by the authors.

Acknowledgments

The authors are grateful to the Ministry of Water and Environment for providing the hydrological data that were used for the simulation of the hydrological model. The authors also extend gratitude to Nsiimire Peter for his contribution to field data collection.

Additional information

Funding

The authors are indebted to the Swedish International Development Agency (SIDA) under the Building Resilient Ecosystems and Livelihoods to Climate Change and Disaster Risks (BREAD) project (Project, 331), which provided funding for the research.

Notes on contributors

Godwin Erima

GODWIN ERIMA is a Doctoral Candidate in the Department of Geography, Geo-Informatics and Climate Sciences, Makerere University, P.O. Box 7062, Kampala, Uganda. E-mail: [email protected]. His research interests include modeling surface water, natural hazard assessment, social vulnerability, and adaptation studies.

Anthony Gidudu

ANTHONY GIDUDU is an Associate Professor in the Department of Geomatics and Land Management, Makerere University, P.O. Box 7062, Kampala, Uganda. E-mail: [email protected]. His research interests include Earth observation applications in monitoring land-cover change dynamics, crop yield forecasting, water quality monitoring, and modeling air pollution and greenhouse emissions.

Yazidhi Bamutaze

YAZIDHI BAMUTAZE is an Associate Professor in the Department of Geography, Geo-Informatics and Climatic Sciences, Makerere University, P.O. Box 7062 Kampala, Uganda. E-mail: [email protected]. His research interests include land use, land degradation, soil erosion, climate change, spatial analysis, soil and water conservation, satellite image analysis, geomorphological mapping, and terrain analysis.

Anthony Egeru

ANTHONY EGERU is an Associate Professor in the Department of Environmental Management, Makerere University, P.O. Box 7062 Kampala, Uganda. E-mail: [email protected]/[email protected]. His research interests include landscape heterogeneity and stochastic landscape processes and indigenous knowledge in pastoral and agro-pastoral communities.

Isa Kabenge

ISA KABENGE is an Associate Professor in the Department of Agricultural and Bio-Systems Engineering, Makerere University, P.O. Box 7062, Kampala, Uganda. E-mail: [email protected]. His research interests include integration of artificial intelligence and Internet of Things in biological systems management, application of biological systems for environmental protection, soil nutrient and moisture interaction and management, evapotranspiration and other energy fluxes of vegetative surfaces, application of GIS to management of natural resources, quantification of plants’ water use and surface energy balance, water and wastewater systems design, operation and maintenance, and renewable energy development and optimization.