Evaluating long-term impacts of land use/land cover changes on pollution loads at a catchment scale.

Evaluating how pollutant loads react to changes in land use/land cover (LULC) is a challenging task due to the intricate relationships among the many elements within a watershed. However, the difficulty in connecting LULC change and nonpoint source (NPS) pollution loads to streams may be lessened by combining hydrological modeling with geospatial tools and multivariate statistics. The objective of this study was to investigate the long-term effects of LULC change on NPS pollution loads in a highly human-dominated catchment, in central Ethiopia. In the study, hydrologic modeling was used to estimate the NPS parameters from multispectral Landsat images, and multivariate statistical techniques were then used to extract major LULC types that explain the variances of NPS loads between 1981 and 2020. The results demonstrated that there were human-induced LULC changes in the area, as the built-up and agricultural landscapes are rising (186.4% and 5.8%, respectively), and shrub and forest lands are decreasing (67.1% and 41%, respectively). As a result of these changes, the concentrations of nitrate (NO3), total P, total N, organic N, and organic P loads were increased by 69.41, 19.83, 18.45, 18.88, and 24.05%, respectively. Reductions in natural vegetation, as well as agriculture intensification, are the major contributors to the NPS pollutant losses to surface water sources. The result also revealed that pollution nutrients are strongly related to deforestation and agricultural land expansion. Proper adaptation strategies should be implemented to minimize the negative impact of LULC changes in the area.

Modeling and optimization of pressure and water age for evaluation of urban water distribution systems performance.

Water loss has become increasingly critical as the severity of the water shortage situation has grown in recent decades. One of the options for reducing water loss in urban water distribution networks is pressure management. The study aimed to evaluate and optimize the existing water distribution system in the city. The proposed methodology is an interactive combination process between an optimization algorithm and WaterGEMS V8i to evaluate the performance of the distribution system. It was observed that, 43.80% of nodes (15-60 mH2O), 5.10% of nodes (15 mH2O), and 51.10% of nodes (>60 mH2O) received pressure during peak hour demand. During low demand periods, only 4.4% of nodes (15-60 mH2O) and 95.60% of nodes (>60 mH2O) received pressure. The water age simulation results revealed that, 51.70% of the pipes were received water age <4.8 h, whereas the other 48.3% of the pipes were received water age <8.6 h during peak hour demand. During low demand periods, 45.58% of the pipes had a water age of less than 4.8 h while the other 54.42% of the pipes had water age of 4.8-20 h. The optimization result showed that after optimization, 4.4% of the nodes with optimum pressure increased to 75.18%, and 95.6% of the nodes decreased to 24.82%. Changing the size of the pipe based on the optimization result, and dividing an area into different pressure zones (adding more reservoirs at the far end of the distribution system) are all ways to improve or upgrade the distribution system.

Land-use/land-cover changes and implications in Southern Ethiopia: evidence from remote sensing and informants.

Understanding land use/cover (LULC) changes and their impacts on the catchment are imperative for proper land management. Hence, useful information concerning responses to LULC changes becomes important to minimize negative impacts on future land uses. The aim of the study was to evaluate the LULC changes and consequences of the change at Bilate catchment from 1986 to 2018. The LULC change evaluations were undertaken by using Landsat images of 1986, 2002 and 2018. Supervised image classification was employed to map the land cover classes. Informant interviews and group discussions with field observations were used to identify the consequences of the changes. Over the past periods, built-up areas, water bodies, cultivation, and barren lands have increased by 0.97, 0.13, 9.27, and 1.36%, respectively. However, the forest and grazing lands have decreased by 8.56 and 3.18% respectively. Exhaustive land cultivation without appropriate management and cultivation of sloppy lands have increased soil erosion and sediment yield to water bodies. A decline in crop yields, livestock products and numbers, and fish population in Lake Abaya are the major implications of LULC change in the catchment. Therefore, to ensure sustainable land use, responsible bodies commit and work closely with communities through participatory approaches.