GIS-Based Sub-Basin Scale Identification of Dominant Runoff Processes for Soil and Water Management in Anambra Area of Nigeria

Abstract

Identifying landscapes having comparable hydrological characteristics is valuable for the determination of dominant runoff process (DRP) and prediction of flood. Several approaches used for DRP-mapping vary in relation to data and time requirement. Manual approaches which are based on field investigation and expert knowledge are time demanding and difficult to implement at regional scale. Automatic GIS-based approach on the other hand require simplification of data but is easier to implement and it is applicable on a regional scale.In this study, GIS-based automated approach was used to identify the DRPs in Anambra area. The result showed that Hortonian overland flow (HOF) has the highest coverage of 1508.3 km 2 (33.5%) followed by deep percolation (DP) with coverage of 1455.3 km 2 (32.3%). Subsurface flow (SSF) is the third dominant runoff process covering 920.6 km 2 (20.4%) while saturated overland flow (SOF) covers the least area of 618.4 km 2 (13.7%) of the study area. The result reveal that considerable amount of precipitated water would be infiltrated into the subsurface through deep percolation process contributing to groundwater recharge in the study area. However, it is envisaged that HOF and SOF will continue to increase due to the continuous expansion of builtup area. With the expected increase in HOF and SOF, and the change in rainfall pattern associated with perpetual problem of climate change, it is paramount that groundwater conservation practices should be considered to ensure continued sustainable utilization of groundwater in the study area.

A GIS based flood vulnerability modelling of Anambra State using an integrated IVFRN-DEMATEL-ANP model

“…The effect of climate change has varied the beginning and cessation of these two seasons in the state ( Okoyeh et al., 2014 ). Heavy and abundant rainfall usually accompany the rainy season with annual rainfall ranging from 1400 mm in the northern part to about 2500 mm in the Southern part ( Fagbohun et al., 2017 ). The state has major surface waters which include springs, lakes, streams, and major rivers such as the southward-flowing Niger River that drains into the Atlantic Ocean, and the Anambra River that drains into the Niger River ( Egboka and Okoyeh, 2019 ; Okoyeh et al., 2014 ).…”

Groundwater quality assessment and characterization of shallow basement aquifers in parts of ado ekiti metropolis, Southwestern Nigeria

“…Groundwater constitutes the major source of utility water in the Ado Ekiti metropolis with sole reliance on it in meeting several demands or purposes [43,47]. Due to the ruggedity of the terrain (peculiar to any basement complex terrain), the runoff amount and infiltration rate are postulated to be high and low, respectively [35]. These underlying basement rocks are mechanically competent (granites more so than the gneisses) and therefore responded to imposed strains by brittle fracture.…”

“…Groundwater in the study area is under influent flow condition (recharged by lateral flow from rivers (Ureje and Orojuda) and their tributaries) during rainy season. The flow and direction of groundwater of the area under study have not been investigated but can be assumed to be localized and in pockets form [35]. This is due to the presence of outcrops interrupting the flat landscape.…”

“…This mode of water contamination is rare and not frequent. Groundwater pollution is mostly attributed to several anthropogenic activities such as irrigation return flow, industrial effluent, high water table in burial grounds and runoff especially in most urban settings of the world [33][34][35][36]. These approaches (hydrochemistry and microbial) have aided the deep understanding and differentiation between rock and water interactions and anthropogenic influences in water systems [37].…”