The Impact of Land Use/Land Cover Change (LULCC) on Water Resources in a Tropical Catchment in Tanzania under Different Climate Change Scenarios

Abstract

Many parts of sub-Saharan Africa (SSA) are prone to land use and land cover change (LULCC). In many cases, natural systems are converted into agricultural land to feed the growing population. However, despite climate change being a major focus nowadays, the impacts of these conversions on water resources, which are essential for agricultural production, is still often neglected, jeopardizing the sustainability of the socio-ecological system. This study investigates historic land use/land cover (LULC) patterns as well as potential future LULCC and its effect on water quantities in a complex tropical catchment in Tanzania. It then compares the results using two climate change scenarios. The Land Change Modeler (LCM) is used to analyze and to project LULC patterns until 2030 and the Soil and Water Assessment Tool (SWAT) is utilized to simulate the water balance under various LULC conditions. Results show decreasing low flows by 6-8% for the LULC scenarios, whereas high flows increase by up to 84% for the combined LULC and climate change scenarios. The effect of climate change is stronger compared to the effect of LULCC, but also contains higher uncertainties. The effects of LULCC are more distinct, although crop specific effects show diverging effects on water balance components. This study develops a methodology for quantifying the impact of land use and climate change and therefore contributes to the sustainable management of the investigated catchment, as it shows the impact of environmental change on hydrological extremes (low flow and floods) and determines hot spots, which are critical for environmental development.Sustainability 2019, 11, 7083 2 of 28 increased agricultural outputs such as food and timber production [9,13]. Several water-related targets of the Sustainable Development Goals (SDGs) are at risk due to land conversions into arable land, especially with regard to SDG 6 (Clean Water and Sanitation) and SDG 15 (Life on Land) [13,14].Several studies investigated the impact of LULCC and climate change on water resources separately [3,15] or simultaneously [16,17]. The results of the studies differ due to several reasons e.g., the type of LULCC, the regional focus, or the time period and model chosen to simulate climate change. However, many studies indicate an increased exposure to hydro-climatic extremes in Eastern Africa [18][19][20][21]. This study exemplarily analyzes LULCC compared to climate change in the Kilombero Catchment in Tanzania and how these affect water resources. The catchment itself is subject to aforementioned LULCC [1,13] and pressure on land resources in the valley is fostered by government plans to implement the Southern Agricultural Growth Corridor of Tanzania (SAGCOT) [22], which is accompanied by a growing population and migration of pastoralists into the valley [23]. SAGCOT follows a green growth approach covering three development clusters in Kilombero, Ihemi, and Mbarali, comprising one third of the mainland of Tanzania [1,24,25]. On the one hand the key clusters are charac...

Long-Term Land Use/Land Cover Change Assessment of the Kilombero Catchment in Tanzania Using Random Forest Classification and Robust Change Vector Analysis

“…The objectives of the project were the assessment of wetland contribution to food security and of the sustainability of current wetland uses, as well as the spatio-temporal extrapolation of results through simulation modeling and scenarios. Knowledge of land cover holds quantified and spatially explicit information as an imprint of socio-economic activity in wetland landscapes and can be integrated in hydrological and agricultural modeling [6]. However, such data is particularly scarce in many African regions.…”

“…Attention was put on the Kilombero area again since it became increasingly important for Tanzania's agricultural production. Recent publications focus on hydrological impacts of LULC change within the Kilombero catchment [6,12,13]. They reveal a high dependency of the wetland on baseflow contribution from the enclosing catchment and demonstrate strong impacts of anthropogenic LULC change on water balance components at subcatchment scale.…”

“…Catchment-wide studies are rare, in particular in East Africa. LULC change in the Kilombero valley was addressed in several case studies [6,12,[17][18][19][20][21][22][23][24][25][26]. Only a few of these studies explored the whole catchment and only few provided an exhaustive evaluation of the generated LULC change maps.…”

Impact of Climate and Land Use/Land Cover Change on the Water Resources of a Tropical Inland Valley Catchment in Uganda, East Africa

“…There exist limited studies [28][29][30][31][32] that have demonstrated the impact of climate and land use change on the hydrological processes in the wetland-catchment nexus in East Africa. Yet, this information is vital to evaluate the possible vulnerability and resilience of these ecosystems to climate change, in particular the impacts of low predictability of precipitation.…”

Testing the Robustness of a Physically-Based Hydrological Model in Two Data Limited Inland Valley Catchments in Dano, Burkina Faso

“…The pairwise comparisons of measured and predicted discharges are commonly utilized to assess model performance in calibration and validation periods using numerical performance indicators such as the coefficient of determination (R 2 ), the Nash-Sutcliffe efficiency (NSE), the Kling-Gupta efficiency (KGE), and graphical method [51][52][53][54][55]. Some authors have modified the pairwise comparisons to account for measurement uncertainties [25,56].…”