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Floods in Ghana have become a perennial challenge in the major cities and communities located in low-lying areas. Therefore, cities and communities located in these areas have been classified as potential or natural flood-prone zones. In this study, the Digital Elevation Model (DEM) of the Accra Metropolis was used to assess the drainage density and elevation patterns of the area. The annual population estimation data and flood damages were assessed to understand the damages and population trend. This research focused primarily on the elevation patterns, slope patterns, and drainage density of the Accra Metropolis. Very high drainage density values, which range between 149 and 1117 m/m2, showed very high runoff converging areas. High drainage density was also found to be in the range of 1117–1702 m/m2, which defined the area as a high runoff converging point. The medium and low converging points of runoff were also found to be ranging between 1702–2563 m/m2 and 2563–4070 m/m2, respectively. About 32% of the study area is covered by natural flood-prone zones, whereas flood-prone zones also covered 33% and frequent flood zones represent 25%. Areas in the Accra Metropolis that fall in the Accraian and Togo series rock types experience high floods. However, the lineament networks (geological structures) that dominate the Dahomeyan series imply that the geological structures in the Dahomeyan series also channel the runoffs into the low-lying areas, thereby contributing to the perennial flooding in the Accra Metropolis.

s Coastal aquifers are complex groundwater bearing zones with multiple ways of interacting with seawater. Understanding of the main controls and evolution of such aquifers is essential for effective management of the groundwater. In this paper, a comprehensive study was conducted to characterize and identify the main factors and processes controlling the groundwater quality in some coastal aquifers through an integrated approach of Principal Component Analysis (PCA), Cluster Analysis (CA), geostatistical analysis and information entropy-based groundwater quality index coupled with detailed hydrogeochemical assessments. The PCA and CA yielded four clusters with distinct hydrogeochemical signatures (Cluster 1 and 2: freshwater influenced by rain, Cluster 3 transition zone and Cluster 4 marine influence/seawater intrusion or aerosol spray). Geostatistical analysis showed a wide variation in salinity from the coast to the inland while piper diagram revealed the evolution of the aquifers from Ca–HCO 3, Ca–Cl which correspond to natural recharge zone in the north, to mixed Ca–Na–Mg–Cl–HCO3 representing transition and Na–Cl towards the coast. The water suitability assessment for drinking using entropy-based groundwater quality index showed that about 59.4%, 20.3%, 7.8%, 2.6%, and 9.9% of the groundwater sample were estimated to be excellent, good, average/medium, poor, and extremely poor water quality. Ion exchange mechanism, dissolution of minerals from the rocks and marine influence are the dominant processes controlling the groundwater chemistry in the area. Recommendations for groundwater resource management and future research needs have also been discussed.

Groundwater is the main water resource which supplies more than half of the residents of Afram Plains. Recent studies show that the aquifer is subject to deteriorating quality from several anthropogenic activities. The aquifer vulnerability to contamination was assessed using the widely known DRASTIC model. This paper aimed to determine the depth-to-water table, identification of the various soil types, topography, recharge rate, and major lithological units in the area. The degree of vulnerability was identified by an index which is computed by superimposition of all the parameters considered for the model. Based on the vulnerability assessment, it was found that, 20.72% (1044.28 km2), 49.78% (2508.91 km2) and 29.50% (1486.80 km2) of the total area was classified as low, moderate and high, respectively. The final vulnerability index was largely influenced by the depth-to-water table, impact of the vadose zone, net recharge and aquifer media parameters. The model was validated with on-ground nitrate concentrations in groundwater in the study area. The DRASTIC model exhibits highly correlated areas in mapping vulnerable regions. The maps produced in this study could be used as a general guide to vulnerability by planners, groundwater managers and decision-makers on the implementation of measures aimed at the protection of this vulnerable resource.

Evapotranspiration is an important component necessary for ensuring efficient management of water resources for every river basin. The Bui Hydroelectric Plant completed early 2014 to provide electricity for the people of Ghana is located within the Black Volta River Basin of West Africa. With the construction of this plant and related developments, there is a need for attention to be paid to the conservation of water resources within this basin. This paper therefore assesses the spatial temporal behaviour of evapotranspiration within the basin from 2001 to 2013 and compares this with the average monthly rainfall estimates from 1983 to 2012. The assessment shows that the average monthly evapotranspiration is within 0 to 150 mm/month for the period assessed. However, significant variation exists between the years with a highly erratic pattern observed. The pattern of the rainfall indicates that the upstream portion of the basin receives lower rainfall compared to the downstream portion of the basin. This pattern is consistent with the overall variation of the evapotranspiration within the basin. This spatial-temporal behaviour is an important factor that needs to be considered by all stakeholders given the anticipated land-use changes expected within the basin coupled with likely future increases in temperatures resulting from climate change. Key words: Evapotranspiration, moderate resolution imaging spectroradiometer 16 (MODIS16), satellite application facility (SAF), Tropical Applications of Meteorology using SATellite (TAMSAT) rainfall, Bui Hydroelectric plant.

Hydrologic modelling lies at the core of hydrology and water resources management. Attempts at gaining a holistic grasp on model robustness, hydrologic theory and processes have inadvertently led to models that are not-well structured or too complex to apply in arid and semi-arid catchments and in Africa, in particular. In view of this, this paper reports on the application of a monthly parsimonious hydrologic model in two catchments in Zimbabwe, the Nyatsime and Upper Save river catchments. The two (2) parameter monthly parsimonious GR2M model was applied. The inputs were rainfall and potential evapotranspiration. Measured discharge was used for calibration and validation. Calibration and uncertainty analysis were done using the Differential Evolution Adaptive Metropolis (DREAM) algorithm. The performance of the GR2M model was evaluated using ten (10) model performance metrics. Parameter indentifiability was analysed on the basis of the shape of the posterior distribution of parameters. Parameter and total uncertainty were analysed in the context of the formal Bayesian DREAM approach. The 10 performance evaluation metrics showed that the model performed satisfactorily during calibration and validation in terms of the overall fit of observed and simulated stream flows, low flows and the runoff volumes. The Nash-Sutcliffe efficiency (NSE) was >0.85, the Kling–Gupta Efficiency (KGE) was >80% and Volume Efficiency was >59% during calibration. Slight performance drops were noted during validation except for the NSE in Nyatsime catchment whilst the KGE remained relatively high. The validation NSE was >0.65, the Kling–Gupta Efficiency (KGE) was >71% and Volume Efficiency was >55%. Calibrated parameters values showed good time-stability and were well identifiable with posterior parameter distributions having Gaussian shapes. Parameter uncertainty, in relation to total uncertainty was low. Parameter uncertainty constituted about 7% of the total uncertainty region. It was concluded that, although the model only had two parameters, the model performed quite satisfactorily in the simulation of monthly flows which makes it a good tool for operational hydrology and water resources modelling, planning and management especially in regions with inadequate data.

The Bui hydropower plant plays a vital role in the socio-economic development of Ghana. This paper attempt to explore the combined effects of climate-land use land cover change on power production using the (WEAP) model: Water Evaluation and Planning system. The historical analysis of rainfall and stream flow variability showed that the annual coefficient of variation of rainfall and stream flow are, respectively, 8.6% and 60.85%. The stream flow varied greatly than the rainfall, due to land use land cover changes (LULC). In fact, the LULC analysis revealed important changes in vegetative areas and water bodies. The WEAP model evaluation showed that combined effects of LULC and climate change reduce water availability for all of demand sectors, including hydropower generation at the Bui hydropower plant. However, it was projected that Bui power production will increase by 40.7% and 24.93%, respectively, under wet and adaptation conditions, and decrease by 46% and 2.5%, respectively, under dry and current conditions. The wet condition is defined as an increase in rainfall by 14%, the dry condition as the decrease in rainfall by 15%; current account is business as usual, and the adaptation is as the efficient use of water for the period 2012–2040.

Our study area is one of the semiarid region of the China with under water stress condition that causes economic damage. The main objective of this study is to apply standardized precipitation evapotranspiration index (SPEI) and to use linear regression to calculate drought conditions in the study area. For this purpose, data from 1980 to 2010 was analyzed at different (1, 6, 12, and 24 months) time scales. Results depicted both dry and wet periods in the study area; occurrence of dry span with different frequency and magnitude was increased over last decades (2000–2010) at most of the stations. Statistical results demonstrated that temperature was decreased in the 1st decade in most of stations but in two decades from 1990 to 2000 and 2001 to 2010, temperature was increased except in Changzhi station. These results could be a future reference for developing information programs about monitoring and early drought information, planning of existing reservoirs, and management of water resources under climate conditions.

The Black Volta basin is one of the most important basins in West Africa that provides support for water supply, irrigation, hydropower and recreation for the communities within this basin. The Tain River basin is a sub-basin within the Black Volta. Most communities within this basin depend on groundwater resources as their main source of water supply. However, the over-growing dependence and limited assessment of the availability of groundwater resources in quality and quantity in the basin have become a worrying factor towards the sustainable management of the resources. The study therefore assessed the quality and quantity of groundwater resources in the Tain River Basin and showed that the total permanent groundwater reserve is estimated as 6.89 x 10 7 m 3 while the total recoverable groundwater as 2.59 x 10 7 m 3 . The total recoverable groundwater forms 38 % of the total permanent groundwater reserve and this is the water available for abstraction and recharging of streams and springs. Both the quality and quantity of groundwater in the basin were found to be adequate according to national standards and World Health Organisation guideline values.

The effects of temperature and rainfall changes on hydropower generation in Ghana from 1960–2011 were examined to understand country-wide trends of climate variability. Moreover, the discharge and the water level trends for the Akosombo reservoir from 1965–2014 were examined using the Mann-Kendall test statistic to assess localised changes. The annual temperature trend was positive while rainfall showed both negative and positive trends in different parts of the country. However, these trends were not statistically significant in the study regions in 1960 to 2011. Rainfall was not evenly distributed throughout the years, with the highest rainfall recorded between 1960 and 1970 and the lowest rainfalls between 2000 and 2011. The Mann-Kendall test shows an upward trend for the discharge of the Akosombo reservoir and a downward trend for the water level. However, the discharge irregularities of the reservoir do not necessarily affect the energy generated from the Akosombo plant, but rather the regular low flow of water into the reservoir affected power generation. This is the major concern for the operations of the Akosombo hydropower plant for energy generation in Ghana.

Potential implications of rainfall variability along with Land Use and Land Cover Change (LULC) on stream flow have been assessed in the Black Volta basin using the SWAT model. The spatio-temporal variability of rainfall over the Black Volta was assessed using the Mann-Kendall monotonic trend test and the Sen’s slope for the period 1976–2011. The statistics of the trend test showed that 61.4% of the rain gauges presented an increased precipitation trend whereas the rest of the stations showed a decreased trend. However, the test performed at the 95% confidence interval level showed that the detected trends in the rainfall data were not statistically significant. Land use trends between the year 2000 and 2013 show that within thirteen years, land use classes like bare land, urban areas, water bodies, agricultural lands, deciduous forests and evergreen forests have increased respectively by 67.06%, 33.22%, 7.62%, 29.66%, 60.18%, and 38.38%. Only grass land has decreased by 44.54% within this period. Changes in seasonal stream flow due to LULC were assessed by defining dry and wet seasons. The results showed that from year 2000 to year 2013, the dry season discharge has increased by 6% whereas the discharge of wet season has increased by 1%. The changes in stream flows components such us surface run-off (SURF_Q), lateral flow (LAT_Q) and ground water contribution to stream flow (GW_Q) and also on evapotranspiration (ET) changes due to LULC was evaluated. The results showed that between the year 2000 and 2013, SURF_Q and LAT_Q have respectively increased by 27% and 19% while GW_Q has decreased by 6% while ET has increased by 4.59%. The resultant effects are that the water yield to stream flow has increased by 4%.

The Densu River Basin is one of the important basins in Ghana. A large number of residents in this basin are dependent on groundwater for their livelihood. However, with the growing population, urbanization and impact of climate change, it is imperative to develop ways to protect and manage the limited groundwater resource that is supporting the communities. As a result, this paper assessed the groundwater vulnerability by comparing two methods – the Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone, and hydraulic Conductivity DRASTIC an the Aquifer Vulnerability Index (AVI). The results show that DRASTIC is more precise and representative of the groundwater vulnerability in the basin. The AVI statistically show a relatively lower risks compared to DRASTIC. It is recommended, AVI which is oversimplified may be useful for larger basins.