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1.
The groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks: an application of natural environmental tracers 
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下载免费PDF全文 Isotope data of precipitation and groundwater in parts of the Voltaian Basin in Northern Ghana were used to explain the groundwater recharge regime in the area. Groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area. It is therefore important to establish the processes and sources of groundwater recharge. δ18O and δ2H data for local precipitation suggest enrichment relative to the Global Meteoric Water Line (GMWL) and indicate that precipitation takes place at a relative humidity less than 100%. The groundwater data plot on an evaporation line with a slope of 5, suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone. This finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates. Groundwater recharge estimates from the chloride mass balance, CMB, method suggest recharge in the range of 1.8–32% of the annual average precipitation in the form of rainfall. The highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area. In the northern parts of the study area, groundwater recharge is lower than 12%. The recharge so computed through the application of the CMB methodology takes on a spatial distribution akin to the converse of the spatial pattern of both δ18O and δ2H in the area. As such, the locations of the highest recharge are associated with the most depleted values of the two isotopes. This observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water. The percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates. At the same time, the amount of water that finally reaches the water table is considerably reduced. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
Sandow Mark Yidana Millicent Obeng Addai Daniel Kwadwo Asiedu Bruce Banoeng-Yakubo 《Arabian Journal of Geosciences》2016,9(17):684
A transient finite difference groundwater flow model has been calibrated for the Nasia sub-catchment of the White Volta Basin. This model has been validated through a stochastic parameter randomization process and used to evaluate the impacts of groundwater abstraction scenarios on resource sustainability in the basin. A total of 1500 equally likely model realizations of the same terrain based on 1500 equally likely combinations of the data of the key aquifer input parameters were calibrated and used for the scenario analysis. This was done to evaluate model non-uniqueness arising from uncertainties in the key aquifer parameters especially hydraulic conductivity and recharge by comparing the realizations and statistically determining the degree to which they differ from each other. Parameter standard deviations, computed from the calibrated data of the key parameters of hydraulic conductivity and recharge, were used as a yardstick for evaluating model non-uniqueness. All model realizations suggest horizontal hydraulic conductivity estimates in the range of 0.03–78.4 m/day, although over 70 % of the area has values in the range of 0.03–14 m/day. Low standard deviations of the horizontal hydraulic conductivity estimates from the 1500 solutions suggest that this range adequately reflects the properties of the material in the terrain. Lateral groundwater inflows and outflows appear to constitute significant components of the groundwater budgets in the terrain, although estimated direct vertical recharge from precipitation amounts to about 7 % of annual precipitation. High potential for groundwater development has been suggested in the simulations, corroborating earlier estimates of groundwater recharge. Simulation of groundwater abstraction scenarios suggests that the domain can sustain abstraction rates of up to 200 % of the current estimated abstraction rates of 12,960 m3/day under the current recharge rates. Decreasing groundwater recharge by 10 % over a 20-year period will not significantly alter the results of this abstraction scenario. However, increasing abstraction rates by 300 % over the period with decreasing recharge by 10 % will lead to drastic drawdowns in the hydraulic head over the entire terrain by up to 6 m and could cause reversals of flow in most parts of the terrain. 相似文献
3.
An evaluation of the genesis and suitability of groundwater for irrigation in the Volta Region,Ghana 总被引：1，自引：0，他引：1
Stable isotope data and concentrations of the major cations and anions of groundwater from the northern part of the Volta
Region, Ghana, were used to determine the source of recharge and the suitability of groundwater in the area for irrigation.
This study finds that the delta deuterium (δD) and delta Oxygen-18 (δ18O) data from the area fall along the global meteoric water line (GMWL). An equation of regression derived for the relationship
between δD and δ18O bears very close semblance to the equation which describes the GMWL. On the basis of this, groundwater in the study area
is probably meteoric and fresh. The apparently low salinities and sodicities of the groundwater seem to support this interpretation.
The suitability of groundwater for domestic and irrigation purposes is related to its source, which determines its constitution.
A plot of the sodium adsorption ratio (SAR) and electrical conductivity (EC) data on a semilog axis, suggests that groundwater
serves good irrigation quality in the area. Sixty percent (60%), 20% and 20% of the 67 data points used in this study fall
within the medium salinity–low sodicity (C2–S1), low salinity–low sodicity (C1–S1) and high salinity–low sodicity (C3–S1)
fields, which ascribe good irrigation quality to groundwater from this area. Salinities range from 28.1 to 1,956 μS/cm, whilst
SAR values fall within the range 0–3. Extremely low sodicity waters of this kind, with salinities lower than 600 μS/cm, have
the tendency to affect the dispersive properties of irrigation soils when used for irrigation. About 50% of the groundwater
in the study area fall within this category and need prior treatment before usage. 相似文献
4.
Bruce Banoeng-Yakubo Sandow Mark Yidana Nti Emmanuel Thomas Akabzaa Daniel Asiedu 《Environmental Earth Sciences》2009,59(4):867-879
Conventional graphical and statistical methods were used with water quality indices to characterize the hydrochemistry of
groundwater from the northern part of the Volta region of Ghana. The objective was to determine the processes that affect
the hydrochemistry and the variation of these processes in space among the three main geological terrains: the Buem formation,
Voltaian System and the Togo series that underlie the area, and to determine the suitability of groundwater from the area
for drinking purposes. The Q-mode cluster analysis reveals three main water groups. The groups established from the Q-mode
HCA appear to indicate different degrees of weathering which could further indicate varying levels of fracturing aquifer hydraulic
properties. R-mode HCA and factor analysis (using varimax rotation and Kaiser Criterion) were then applied to determine the
significant sources of variation in the hydrochemistry. This study finds that groundwater hydrochemistry in the area is controlled
by the weathering of silicate and carbonate minerals, as well as the chemistry of infiltrating precipitation. Mineral activity
diagrams for the CaO–Na2O–Al2O3–SiO2–H2O and CaO–MgO–Al2O3–SiO2–H2O systems plotted for the area indicate stability in the smectite field and attribute hydrochemistry to the weathering of
silicate minerals. Silicate mineral weathering and the effects of precipitation appear to be pervasive among all the three
main geological terrains, whereas carbonate weathering is localized among the Voltaian aquifers. Cation exchange does not
appear to play a significant role in the hydrochemistry but mild Water quality indices (WQI) were calculated for the samples
using the concentrations of Na+, Ca2+, Mg2+, Cl−, NO3
−, F−, and EC at the various sample locations. The WQI values indicate that groundwater from the study area is of excellent quality
for drinking purposes. WQI values from groundwater samples are averagely higher than samples taken from surface water sources
in the area. This implies that geology has had an impact on the WQI of groundwater in the area. 相似文献
5.
Sandow Mark Yidana Samuel Ganyaglo Bruce Banoeng-Yakubo Thomas Akabzaa 《Journal of African Earth Sciences》2011,59(2-3):185-194
A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10?5 m/d to 7.14 × 10?4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast–southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization. 相似文献
6.
7.
Nelson Attandoh Sandow Mark Yidana Aliou Abdul‐Samed Patrick Asamoah Sakyi Bruce Banoeng‐Yakubo Prosper M. Nude 《水文研究》2013,27(11):1664-1676
Groundwater resources play a pivotal role in the rural water delivery system in Ghana. The hydrogeological system of Middle Voltaian terrain was simulated using available data on hydraulic heads and boundary conditions. The objective was to characterize the general groundwater flow pattern and provide local estimates of the distribution of hydraulic conductivity and recharge fields. The results suggest a predominant NE–SW flow direction, which ties in with the general regional structural trend and indicates that the hydrogeological conditions of the rocks are controlled by structural entities created in the wake of fracturing and/or weathering of the rocks whose primary permeabilities are considerably reduced because of high compaction and low‐grade metamorphism. Calibrated hydraulic conductivities range between 1.90 and 10.81 m/d. The spatial distribution appears to reflect the intensity of fracturing and/or weathering of the rock and the proportion of the clay fraction of the weathered zone. Vertical groundwater recharge has been estimated to range between 0.3% and 4.1% of the annual rainfall. This recharge rate is quite low and reflects the imperviousness of the thick overburden because of high clay content in some places and high compaction in others. Despite this apparently low recharge rate, groundwater resources potential in the area appear to be high, and increased abstraction from existing abstraction wells by up to 50% does not appear to register significant effects on groundwater budgets at the simulated recharge rates. This suggests that the well yields are much lower than the potential of the aquifer system. The apparently low yields might be associated with poor well development and the choice of inappropriate well completion materials. This study recommends a monitoring system to be developed for a much more regional groundwater flow simulation under transient conditions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
Groundwater flow modeling and particle tracking for chemical transport in the southern Voltaian aquifers 总被引：1，自引：1，他引：0
Sandow Mark Yidana 《Environmental Earth Sciences》2011,63(4):709-721
Groundwater is the major source of water supply for most uses in the rural settlements in Ghana. A groundwater flow model
was calibrated for some aquifers of the southern Voltaian sedimentary system under steady-state conditions. The objective
was to determine estimates of the hydraulic conductivities of the different hydrostratigraphic units of the southern Voltaian,
and the distribution of recharge from precipitation. Data on the stable isotopes of oxygen and hydrogen from the study area
suggest that groundwater recharge in the area is from rainfall. The calibrated steady-state model suggests that aquifer hydraulic
conductivities in the study area range from 1.19 to 6.3 m/day. Hydrostratigraphic unit specific hydraulic conductivities are
discussed. The calibrated recharge ranges from 3.81e−05 m/day to 6.0e−04 m/day, which represents 0.9–6% of the precipitation
in the form of rainfall. Six distinct flowpaths have been defined using particle tracking. The particle tracking simulation
suggests travel times in the range of 380 to 5,199 years from recharge areas to discharge areas along the flowpaths identified.
A contaminant dropped at the recharge areas in the central sections of the model area would travel at these rates along the
flowpaths, assuming that advection is the dominant transport process. Inverse geochemical modeling indicates the dissolution
of albite, K-feldspars and anorthite, respectively, along flowpaths I and IV. The inverse modeling along flowpaths I and IV
suggest the dissolution of albite, K-feldspar and anorthite, respectively, at 1.085e−06, 3.16e−08 and 3.168e−07 mmol/year. 相似文献
9.
Sandow Mark Yidana Bruce Banoeng-Yakubo Abdul-Samed Aliou Thomas M. Akabzaa 《水文科学杂志》2013,58(6):1168-1183
Abstract Groundwater is a priceless resource in the economies of the rural populations in northern Ghana. A combination of multivariate statistical and spatial analytical techniques was applied to groundwater data from the Voltaian and Birimian aquifers in parts of northern Ghana. The objective was to classify the groundwater quality control parameters and determine whether the aquifers deliver groundwater of acceptable quality for domestic and commercial irrigation purposes. It was found that groundwater quality is dominated by the weathering of accessory minerals that are predominant in the Obosum and Oti beds of the Middle Voltaian in the north, and incongruent silicate mineral weathering ranks second among the major causes of variation. The two processes account for over 70% of the total variance in the hydrochemistry and interpolation maps generated for these two major factors are discussed. The mineral weathering and dissolution processes are less apparent within the Birimian aquifers. Four spatial groundwater types were distinguished by differences in EC and pH, which are high among the water types within the Obosum and Oti beds, and generally low within the Birimian aquifers. Mineral stability diagrams suggest that montmorillonite is the most stable clay mineral phase in the system, a significant finding in terms of cation exchange processes. This, in turn, has affected the irrigation quality of groundwater from the aquifers in the area. Our findings suggest that the Birimian aquifers are more suitable for irrigation, due to generally low salinities and sodicities, and those associated with the Obosum and Oti beds of the Middle Voltaian are less suitable. Editor D. Koutsoyiannis; Associate editor Y. Guttman Citation Yidana, S.M., Banoeng-Yakubo, B., Aliou, A.-S., and Akabzaa, T., 2012. Groundwater quality in some Voltaian and Birimian aquifers in northern Ghana—application of mulitvariate statistical methods and geographic information systems. Hydrological Sciences Journal, 57 (6), 1168–1183. 相似文献
10.
Acid rock/mine drainage and metal leaching constitute major environmental management risks in the mining industry. This paper
assesses the environmental risks due to acid rock/mine drainage, and the metal leaching potential of multiple mines of gold
and manganese on the Ankobra River Drainage Basin in Southwestern Ghana. The basin is a hub of mining activity in Ghana, hosting
several mines. A combination of mineralogical, and static geochemical acid drainage predictive investigation of overburden
of varied geological units, complimented with hydrochemical drainage quality analysis was used to assess potential environmental
risks posed by acid-generating lithologies and mine spoil. Mineralogical investigations revealed sulphide-bearing lithological
units with profound compositional variations due to the incorporation of potentially toxic heavy metals and metalloids, in
association with carbonates and silicates. Accounting Base Accounting (ABA) and Net acid generation potential pH (NAGpH) tests
delimited two tailing sites as potentially acid generating with NAGpH of 3.5 and 4.8, respectively. Five other samples, representing
specific lithological units in the stratigraphic sequence, with net acid neutralization potential ratio (NNPR) less than 5.0,
were classified as being potentially acid generating according to the categorization requirement of the US Forestry Service.
The rest of the samples exhibited moderate to very strong buffering capabilities. The assessment also evaluated drainage quality
of the network of streams and rivers constituting the basin and identified sources of drainage contaminants. Acidic waters
emanate from identified acid generating sources, while high metal load regimes were identified with both low pH waters and
high pH regimes, coincident with high sulphide and carbonate alteration sites, respectively. The study results show that Zn,
Cu, Ni, As, Co, Sb, SO4
2−, pH, alkalinity and conductivity are essential and adequate parameters in routine environmental risk monitoring programmes
of mines in the area. Sites characterized by low pH (<5.5) with high sulphate and metal ions are suggestive of acid mine drainage,
while sites with high pH (>7.5), metal ions and sulphate are suggestive of net acid neutralizing. 相似文献