Hydrological classification of the Besease inland valley bottom in Ghana for crop production using the water table fluctuation method (original) (raw)
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Trend in ground water table fluctuation was investigated on an experimental field of 18070.2 m 2 between June and March of a following year. Five Piezometers were used to monitor the depth of water table at different locations. Findings indicated a depth of water table fluctuation between 0.4 cm above the soil surface and 200 cm below surface. Further analysis carried out on possible relationship between depth of water table and time indicated a non linear polynomial of second order degree (Y = a + b 1 X + b 2 X 2) with 0.84 as the average regression coefficient (R 2). Trend in depth of water table (from ground surface) decreases with increasing rainfall from July to September but increases from September to March as rainfall decreases from September to November. Nevertheless, the sharp decline in rainfall between September and October do not translate to increase in depth of water table, this could be due to over saturation of soil in September that recharged the valley in October. The relationship between rainfall and depth of water table from the ground surface is statistically significant with regression coefficient of 73%.
Modelling Groundwater Flow of the Besease Inland Valley Bottom in Ghana
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The harsh climate, shallow and erodible soils of low fertility uplands have led to farmers extending their cultivable areas to wetlands for optimal crop production since these systems have the potential for irrigation in the dry season. Inland valleys have been cited as having high potential for development of rice-based, small-holder farming systems at the village level, due to their specific hydrological conditions and relatively high soil fertility. This paper applies a 3D groundwater flow model, PM-WIN MODFLOW to simulate the groundwater heights of the two layered alluvial aquifer of the Besease Inland Valley Bottom. Groundwater recharge estimates from the watertable fluctuation method was used as the recharge input into the model. The results showed that groundwater levels ranged from 259.10-259.97 m in the wet season and 258.19 -258.86 m in the dry season for the simulation period. It also exhibited a form of interaction between the inland valley wetland and the bordering Oda ...
Fluctuation of Groundwater Levels and Recharge Patterns in Northern Ghana
Evaluating groundwater levels and recharge patterns is part of sustainably managing the water supply and predicting the possibility of water shortages, especially in light of climate change, extreme events (floods/droughts), increasing population and development. In the northern region of Ghana, groundwater is increasingly relied upon as a source of potable water for rural populations, but seasonal and inter-annual fluctuations of groundwater levels and recharge patterns are not always known. The fluctuation of groundwater levels on a seasonal basis shows that groundwater levels at all sites increase in response to seasonal precipitation. On an annual basis, all sites show an overall net decline of groundwater levels over the study period, which may be associated with below-average departures of precipitation during five of the seven study years. The variability of recharge patterns among five sites is attributed to the spatio-temporal variability of precipitation and hydrogeologic site uniqueness. The overarching potential benefit of this study is to facilitate OPEN ACCESS Climate 2015, 3 2 closing knowledge gaps and contribute to a foundation for a more robust evaluation of groundwater resources in the area, especially as more data become available.
Rising water tables is one of the major problems affecting irrigation and agriculture in general, hence, regular investigation of the trend of groundwater fluctuation especially within 'fadama' lands is necessary to forestall incidences of flooding and salinization which are harmful to arable soils. Groundwater fluctuation was monitored between February and September, using chalk-dusted graduated steel tapes at five (5) piezometric locations in a small-scale fadama irrigation farm, in the Niger-Benue Confluence, Lokoja-Nigeria. It was observed that the mean monthly depth of water table fluctuates between 2.03m bgl and 0.022m agl in the period under review. Statistical analysis of data collected show that the trend of fluctuation obeys a third order hyperbolic function (with R 2 = 0.98). Findings imply that the land is critically waterlogged between February and September, with rainfall depth significantly affecting groundwater fluctuation, and will be prone to salinity hazard overtime. There may be need to carry out further investigations on the hydrological characteristics such as hydraulic conductivity, infiltration and evapotranspiration for the area; these may inform the need to design appropriate measures for the water resources management in this area; such as installation of drainage structures/facilities to check the flooding and/or drilling of more shallow tubewells for irrigation purposes in months of less rainfall.
Groundwater level monitoring and recharge estimation in the White Volta River basin of Ghana
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Recharge quantification is an important pre-requisite for effectively managing groundwater resources as recharge estimates are needed to determine sustainable yields of groundwater aquifers for rational and sustainable exploitation of the resource. In this study, the water table fluctuation method has been applied in the White Volta River basin of Ghana (approx. 46,000 km 2 ) to estimate seasonal fluctuations in groundwater levels in the basin and subsequently to estimate recharge to the groundwater for the 2006 and 2007 water years. Results show high seasonal and spatial variability in the water level, with a range of 1240-5000 mm in 2006, and 1600-6800 mm in 2007. Seasonal rainfall was found to be the main source of recharge to the aquifers in the basin as water level rise occurred only in the rainfall season. Recharge to groundwater in the White Volta basin was estimated to vary between 2.5% and 16.5% of the mean annual rainfall, with a mean recharge of 7-8%.
Quantification of groundwater recharge differs in their methods of estimation and therefore gives variable recharge estimates whenever a groundwater system is evaluated. Quantifying the fraction or the percentage of infiltrated water which reaches the watertable is a key factor in any sustainable planning scheme for groundwater resource management. The watertable fluctuation method was used to evaluate the seasonal and annual variations in water level rise and to estimate the groundwater recharge. The results showed that annual water level rise ranged from 1105-3115 mm in 2009 and from 397-3070 mm in 2010. A range of specific yields have been extracted from the values determined from the soil textural classification triangle. The estimated recharge for the study area ranged from 133-467 mm for the fourteen (14) piezometers installed for the study, representing 9- 31% of the 2009 annual rainfall and 47.6-427.9 mm, in 2010 representing 4-34 % of the annual rainfall. The area-weighted ...
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Evaluating groundwater levels and recharge patterns is part of sustainably managing the water supply and predicting the possibility of water shortages, especially in light of climate change, extreme events (floods/droughts), increasing population and development. In the northern region of Ghana, groundwater is increasingly relied upon as a source of potable water for rural populations, but seasonal and inter-annual fluctuations of groundwater levels and recharge patterns are not always known. The fluctuation of groundwater levels on a seasonal basis shows that groundwater levels at all sites increase in response to seasonal precipitation. On an annual basis, all sites show an overall net decline of groundwater levels over the study period, which may be associated with below-average departures of precipitation during five of the seven study years. The variability of recharge patterns among five sites is attributed to the spatio-temporal variability of precipitation and hydrogeologic site uniqueness. The overarching potential benefit of this study is to facilitate
Groundwater recharge estimation using water table fluctuation and empirical methods
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The reliable estimation of groundwater recharge is fundamental to the appropriate use of groundwater resources. Shallow groundwater resource quantification for irrigation in highland regions remains challenging. Specifically, in the humid Ethiopian highlands, only limited research has been done on groundwater recharge estimation. Despite the various techniques used to determine recharge, the objective of this study was to better understand natural groundwater recharge using water table fluctuation (WTF) and empirical methods in the sub-humid Ethiopian highlands. The Ene-Chilala watershed was selected for this study. Precipitation, infiltration rate, and piezometric water levels were measured. Precipitation was measured over a 4-year period (2013–2016), whereas infiltration and the groundwater table were measured over a 1-year period (2014). Recharge rates using WTF were determined from the three slope positions and the median of all piezometers for the whole watershed. Infiltration ...
Hydro-period dynamics of some inland valley agroecosystems in southwest Nigeria
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The potential use of inland valley ecosystems (a category of wetlands) for cropping has not been fully exploited due to their heterogeneity in hydrology, morphology, soil types and agro-economy. The study employed the hydro-period approach to investigate the dynamics of surface waters of six inland valley sites. Hydrographs and hydro-periods of the sites were determined using water-level fluctuation data collected using staff gages. Results show that water level rose gradually from the beginning of the rain season, peaked at the end of the season, and receded gradually until the hydrological peak of dry season in amphitheatre and valley-side valley types. In the low depression valleys, the plots indicate a more instantaneous response to rainfall events with little groundwater flow. The work concluded that amphitheatre and valley-side valleys types are perennial with high base flows and low flow variability, and hence should be suitable for year-round cropping with little or no application of irrigation. On the other hand, the stage-duration curves of the depression valleys are characteristics of seasonal streams occurring in low-sloped topography with largely rain-caused floods, low base flow, and high flow variability. Application of irrigation may be required for dry season cropping in these valleys.
Hydrological Processes, 2018
Inadequate knowledge exists on the distribution of soil moisture and shallow groundwater in intensively cultivated inland valley wetlands in tropical environments which are required for determining the hydrological regime. This study investigated the spatial and temporal variability of soil moisture along four hydrological positions segmented as riparian zone, valley bottom, fringe, and valley slope in an agriculturally used inland valley wetland in central Uganda. The determined hydrological regimes of the defined hydrological positions are based on soil moisture deficit calculated from the depth to the groundwater table. For that, the accuracy and reliability of satellite-derived surface models, SRTM-30 m and TanDEM-X-12m, for mapping microscale topography and hydrological regimes is evaluated against a 5m DEM derived from field measurements. Soil moisture and depth to groundwater table were measured using Frequency-Domain-Reflectometry sensors and piezometers installed along the hydrological positions, respectively. Results showed that spatial and temporal variability in soil moisture increased significantly (p<0.05) towards the riparian zone, however, no significant difference was observed between valley bottom and riparian zone. The distribution of soil hydrological regimes, saturated, near and non-saturated regimes does not correlate with the hydrological positions. This is due to high spatial and temporal variability in depth to groundwater and soil moisture content across the valley. Precipitation strongly controlled the temporal variability while microscale topography, soil properties, distance from the stream, anthropogenic factors, and land use controlled the spatial variability in the inland valley. TanDEM-X DEM reasonably mapped the microscale topography and thus soil hydrological regimes than SRTM DEM. The findings of the study contribute to improved understanding of the distribution of hydrological regimes in an inland valley wetland which is required for a better agricultural water management planning.