Soil erosion is one of the most critical environmental hazards that causes land degradation and water quality challenges. Specifically, this phenomenon has been linked, among other problems, to river sedimentation, groundwater pollution and flooding. This paper assesses the susceptibility of Orashi River Basin (ORB) to soil erosion for the purpose of erosion control measures. Located in the South Eastern part of Nigeria, the ORB which covers approximately 413.61 km² is currently experiencing one of the fastest population growth rate in the region. Analysis of the soil erosion susceptibility of the basin was based on four factors including; rainfall, Land use/Land cover change (LULC), slope and soil erodibility factor (k). The rainfall was assumed to be a constant and independent variable, slope and soil types were categorised into ten (10) classes each while the landuse was categorised into five classes. Weight was assigned to the classes based on the degree of susceptibility to erosion. An overlay of the four variables in a GIS environment was used to produce the basin susceptibility to soil erosion. This was based on the weight index of each factors. The LULC analysis revealed that built-up land use increased from 26.49 km² (6.4 %) in year 1980 to 79.24 km² (19.16 %) in 2015 at an average growth rate of 1.51 km² per annum while the light forest decreased from 336.41 km² (81.33 %) in 1980 to 280.82 km² (67.89 %) in 2015 at an average rate 1.59 km² per annum. The light forest was adjudged to have the highest land cover soil erosion susceptibility. The steepest slope ranges between 70 and 82° (14.34 % of the total land area) and was adjudged to have the highest soil susceptibility to erosion. The total area covered of the loamy soil is 112.37 km² (27.07 %) with erodibility of 0.7. In all, the overlay of all the variables revealed that 106.66 km² (25.70 %) and 164.80 km² (39.7 %) of the basin has a high and very high susceptibility to soil erosion. The over 50 % high susceptibility of catchment has serious negative implications on the surface water in terms of water quality and downstream siltation with great consequences on biodiversity and ecosystem services including domestic and industrial usage.

The Sokoto-Rima basin defines the natural and socioeconomic lifeblood of northwestern Nigeria. Its agrarian nature is an indication of significant dependence on the supply of ecosystem services from its various rivers, streams, and wetlands. However, nitrogen (N) and phosphorus (P) constitute a great portion of chemical fertilizers used to enhance crop yields and poor management of these portend great threats for water quality. The overarching objective of this study was to examine the extent of spatial variation of nutrient dynamics in the Sokoto-Rima basin between 1992 and 2015 using the nutrient delivery ratio (NDR) model of InVEST (Integrated Valuation of Ecosystem Service and Tradeoffs) software. Land use/landcover, precipitation, digital elevation, and biophysical variables were the principal datasets employed as model input. The result of the study showed that the surficial N load is almost 15-fold of P in the Sokoto-Rima basin. Over the period of study, cultivated areas and rivers were spatially detected as nutrient sources and sinks respectively. The subsurface nutrient load is dominated by P while the amount of N load is insignificant. The trend of nutrient export is linearly defined: with 0.87% and 1.7% increase in N and P export respectively during 1992-2015. N and P exports vary spatially with a north-south increase-decrease index. Critical length and threshold are highly sensitive to changes in the parameterization of the NDR model. Thus, synergistic cultivation practices such as agroforestry should be extended to existing crop cultivation complexes to curtail nutrient enrichment in the Sokoto-Rima basin and ensure environmental sustainability.

Introduction: Human activities exert great pressures on the environment which in turn cause environmental stresses of various intensities depending on the factors involved and the sensitivity of the receiving environment.Objective: This study examines the effects of anthropogenic activities along the sub-urban lagoon fragile coastal ecosystem using DPSIR framework.Results: The results show that the study area has undergone a tremendous change between 1964 and 2015 with the built up area increasing to about 1,080 ha (17.87%) in 2015 from 224 ha (1.32%) in 1964 at an average growth rate of 16.78ha per annum. The nature of the degradation includes an increasing fragility of the ecosystem through the emergence and expansion of wetlands, flooding and erosion as well as a reduction in the benefits from the ecosystem services. Population growth, between 2006 and 2015 for Ikorodu LGA, estimated at 8.84% per annum serves as the most important driving force in reducing the quality of the environment. This is in addition to Pressures emanating from anthropogenic activities. The state of the environment shows continuous resource exploitation (fishing and sand mining) with the impacts of the pressures coming from water pollution, bank erosion, biodiversity loss and flooding. Although there has been a strong policy formulation response from the government, weak implementation is a major challenge.Recommendation: The study recommends public awareness campaigns and the implementation of existing policies to ensure a sustainable sub-urban lagoon coastal environment..

Understanding the dynamics of water yield as relates to water balance is vital for the functioning of ecosystems as well as model-based computation of their respective ecosystem services. In dryland regions such as the Sokoto-Rima basin, this is of cogent importance for effective planning, and management of its scarce water resources. In this study, we assess the spatiotemporal dynamics of quick flow (QF), local recharge (LR), and baseflow (B) between 1992 and 2015 using the Seasonal Water Yield (SWY) model of InVEST (Integrated Valuation of Ecosystem Service and Tradeoffs) software. Pre-classified land cover, rainfall, satellite-derived evapotranspiration, digital surface topography, and HYSOGs 250m soil datasets were used as software data inputs. The result of the study showed that QF, LR, and B depict similar spatial distribution with peak values generated within water-bearing land cover areas particularly water bodies and wetlands. QF was highest in 2002 (1,293.6 mm) while there were reductions in the subsequent years – 2012 and 2015. Similar patterns were observed in LR and B with much lower values. The temporal trend for the 23-year period of the study showed that QF had an increasing rate of 85,331 mm while decreasing rates of 56,131 mm and 27,597 mm were detected for LR and B respectively. Three key parameters – alpha, beta, and gamma showed evidence of sensitivity to changes in values. These water balance transactions provided an opportunity to review the impact of the sensitivity of the land cover, climate, and hydrogeological factors on water resources management particularly freshwater accounting in the Sokoto-Rima basin of the northwestern part of Nigeria.

Soil erosion is an important morphological process contributing to land degradation in humid tropical environments. Information on soil loss is essential for selecting appropriate control measures to reduce on-site soil loss and its off-site effects, especially in-built environments. The objective of this study was, therefore, to estimate the volume of soil loss due to gully erosion in the Iwogban urban catchment area in Ikpoba-Okha local government in Benin City, Edo State, Nigeria, using the Revised Universal Soil Loss Equation (RUSLE) Model in the Geographic Information System GIS) environment. The result showed that about 30.2895 tons/ac/yr of soil is lost in the watershed, which exceeds the RUSLE tolerance value (T-value). If the computed soil loss exceeds the T-value, erosion is considered excessive, and improved erosion control is needed. Morphologically, the gully is u-shaped and highly active at the gully's head and side walls. Effective management practices such as re-channelizing the watercourse, partial reclamation of the gully head, introduction of vegetative cover, and afforestation are highly recommended.