Shallow Hard Rock Aquifer Research Articles

Multitracer approach towards an improved understanding of shallow hard rock aquifers and a more sustainable groundwater management, case of Yaounde, Cameroon

Multitracer approach towards an improved understanding of shallow hard rock aquifers and a more sustainable groundwater management, case of Yaounde, Cameroon

Benefits, equity, and sustainability of community rainwater harvesting structures: An assessment based on farm scale social survey

Rainwater harvesting systems (RWHs) are implemented globally to bridge the frequent water supply-demand gaps. This study explores, through farmer household surveys (n = 492), how farmers perceived the benefits of RWHs, the equitability of benefits, and the role of contextual and psychological factors towards the behaviour of maintaining such systems. The study is carried out in a semi-arid catchment in the Indian state of Gujarat where RWHs, in the form of Check dams (CDs), have been implemented extensively. Results show that the benefits of CDs are perceived in good rainfall years through enhanced availability of water for expanding crops and irrigated areas. Farmers reported limited benefits of CDs in dry years. This is because of limited runoff and no carryover of stored groundwater, due to underlying shallow hard rock aquifer with little primary porosity, from wet years to dry years. Overall, ∼ 40%–50% of sampled farmers reported no benefits from CDs and the benefits decreased with distance. This reflects a spatially inequitable distribution of benefits skewed towards the farmers nearest to the CDs. The sustainability of CDs is a challenge with already ∼40% of CDs reportedly not working and 72.8% of farmers reported doing no maintenance activity. This is because 91.2% of farmers reported playing no role in its construction. The results show contextual (participation during construction, economic indicators) and sociopsychological factors (attention to CD condition, maintenance effort) significantly affect the behaviour towards maintaining the CDs. This highlights the need to complement RWHs with wider drought management and water demand management interventions to achieve drought resilience, and adherence to project exit protocols to secure the sustainability of investments.

Evaluation of heavy metal contamination and human health risk using geo-statistical techniques in selected shallow hard rock aquifers of southwest India

Groundwater is a vital natural resource for drinking and irrigation purposes in India. Heavy metal contamination in groundwater is a global concern and leads to potential health risks to humans and the ecosystem. The aim of this study is to evaluate heavy metal contamination and human health risk in hard rock aquifers of southwest India. Groundwater samples were collected from open wells during the pre-monsoon and monsoon seasons. Heavy metal analysis was conducted using ICP-MS. Geostatistical interpolation technique was applied for spatial analysis. The results revealed that north-west region of the study area have a significant concentration of heavy metals in both the seasons due to intensive agricultural activity. Human health risk assessment in the study area revealed that children are more prone to health risks than adults and infants. Further, this study suspects moderate risk to the groundwater dependent ecosystem. Factor analysis indicates that heavy metals present in groundwater were derived from both geogenic and anthropogenic factors during both seasons. The study concludes that regular monitoring of groundwater is essential to control heavy metal contamination from anthropogenic activities. The heavy metal data obtained from this study can be a valuable database for decision makers to choose the areas of concern, for future water management plans.

How can resource-level thresholds guide sustainable intensification of agriculture at farm level? A system dynamics study of farm-pond based intensification

Sustainable intensification (SI) of agriculture combines the dual goals of increasing productivity while staying within safe limits of resource use. In practice, how can thresholds which operate at resource scale guide intensification driven by social, economic and biophysical factors at the farm scale? In this paper, we present the case of agricultural intensification in the shallow hard-rock aquifer region of western India to illustrate how cross-scale feedback effects are crucial determinants of not only the resource sustainability and farm productivity but also of social dimensions of SI such as equity and justice. Supported by private investment in plastic-lined farm-ponds, the increasing shift to horticulture in the study area raises questions about the sustainability of the practice. We use a socio-hydrological lens and develop a system dynamics model to analyze how the growing technology-mediated intensification may lead to SI. We find that from a static farm-level view, the plastic-lined farm-pond is beneficial in shielding farmers from droughts and in enhancing productivity. However, when within and across scale socio-hydrological dynamics are considered, the practice is found to instead aggravate the drought impact on the community. This happens when intensification level accelerates, driven by aspiration and vulnerability induced feedbacks, resulting in groundwater demand exceeding the system threshold. In practice, SI is complicated by the fact that this threshold for safe groundwater use is dynamic. In drought years the carrying capacity falls significantly, so that even a low level of intensification may tip the system resulting in a tragedy of the commons. Therefore, achieving SI requires seasonally agile intensification which retains the adaptive capacity of farmers instead of locking them into fixed annual irrigation requirement in a highly uncertain and resource-scarce environment. We thus conclude that the recognition and translation of resource level thresholds to an actionable level is key to practicing SI.

Health risk assessment of nitrate and fluoride toxicity in groundwater contamination in the semi-arid area of Medchal, South India

Hydrogeochemical controlling variables for the high rate of groundwater contamination in a shallow hard rock aquifer of the semi-arid region of Medchal District, Telangana State, South India, and its associated health risk to children and adults were studied in detail. A total of 56 groundwater samples were analysed for major ion chemistry in pre- and post-monsoon seasons in 2019 year. Spatial distribution, hydrochemical facies, water–rock interaction, health risk assessment, carcinogenic risk, and principal component analyses were carried out to assess the water quality. Spatial distribution of nitrate and fluoride concentrations, high values were observed in the northern, southern, central, and south-western parts of the region. In terms of NO3−, about 88% and 63% and for F− 45% and 32% of the groundwater samples are non-acceptable limits of nitrate 45 mg/l and fluoride 1.5 mg/l during pre- and post-monsoon seasons, respectively. Modified Gibb’s plot showed the majority of the area is dominated by rock dominance and evaporation mechanisms. Statistical analysis reveals that water chemistry is governed by weathering of feldspar minerals and the cation exchange reaction mechanism. The petro-graphical studies revealed the dominance of plagioclase, orthoclase, quartz, biotite, apatite, and hornblende minerals in the host rock. The factor analysis results reveal that the geogenic and anthropogenic activities contribute to groundwater chemistry. Health risk assessment was carried out by calculating the hazard quotient (HQ) on the basis of intake exposure of groundwater, as per the USEPA. Results were obtained for total hazard index value greater than 1 for adults and children, which causes non-cancerous health effects.

Groundwater flow patterns, hydrogeochemistry and metals background levels of shallow hard rock aquifer in a humid tropical urban area in sub-Saharan Africa- A case study from Olézoa watershed (Yaoundé-Cameroon)

Study regionOlézoa watershed, Yaoundé-Cameroon, Central Africa Study FocusThis study aimed to determine the hydrogeological characteristics of shallow hard rock aquifer and the environmental levels of heavy metals in an urbanized equatorial region. Physico-chemical parameters and heavy metals were determined on 25 groundwater samples and analyzed using conventional hydrochemical methods, multivariate analysis, heavy metal pollution index (HPI) and natural background levels (NBL). New Hydrological Insights for the RegionHydrogeological functioning is not marked by a mass of basal groundwater with a low hydraulic gradient Hydrochemical facies were predominantly Ca-Mg-Cl, HCO3-Ca-Mg and Ca-Cl type, which were controlled water-rock interaction, cation exchange, dissolution of silicates and anthropogenic activities. Multivariate analysis did not show very significant hydrochemical spatial zonation but the first major component can be used as an indication of the groundwater flow direction. Vertically, a three-part structure around depths of 1 m and 3−7 m were identified and associated with local and intermediate flow systems at the Olézoa watershed-scale.HPI showed short range variations similar to that of EC, suggesting compartmentalization of the shallow aquifer on a small scale. Thus, a preliminary conceptual model describing groundwater dynamics has been proposed. NBL and median HPI values indicate a serious concern in terms of groundwater qualitative potential and the urgency of regular monitoring of heavy metals in groundwater in this urbanized part of sub-Saharan Africa.

Monsoon impact on groundwater chemistry and geochemical processes in the shallow hard rock aquifer

Impact of monsoon recharge on groundwater chemistry and geochemical processes was evaluated using geochemical methods in the shallow hard-rock aquifer, southern India. Groundwater samples were collected from Salem city and its outskirts during pre-monsoon (PRM) and post-monsoon (PM) seasons and analysed for major and minor ions. Results suggest that during PRM, the average concentration of TDS, major ions and electrical conductivity (EC) in groundwater are higher than the PM season except for Na+ and HCO3–. The major water types also varied with seasons (PRM: NaCl > CaMgCl > CaHCO3; PM: CaHCO3 = NaHCO3 = NaCl). Pearson correlation analysis indicates that Cl− and SO42− show a strong positive correlation with EC, TDS, TH and major cations during PRM season whereas HCO3– and NO3– have a strong positive correlation with most of the ions during PM season. Before monsoon, the water chemistry is governed by the weathering of carbonate and silicate minerals, reverse ion exchange and evaporation processes, which resulted in high EC, TDS, TH and major ions in the groundwater. After the monsoon, the water chemistry is regulated by the mineral weathering, cation exchange and dilution processes. Geochemical modelling studies indicate that groundwater is saturated and oversaturated with carbonate minerals and undersaturated with sulphate and chloride minerals. During monsoon, the recharging water flushed the weathered layer and dissolved the soil CO2 in the vadose zone, which subsequently enhanced the concentration of Na+ and HCO3– in the aquifer. Further, the high concentrations of Cl−, SO42- and NO3– imply that the aquifer is polluted by surface contamination sources. After the monsoon, NO3– implies that monsoon recharge facilitated the pollutant movement from surface to the aquifer. Hence, a proper aquifer management plan is required to protect this aquifer and to provide clean and safe drinking water to the local community.

Artificial recharge of a shallow hard rock aquifer as a climate change mitigation method: model solution from the Czech Republic

Drought has always been one of the crucial water management issues especially in a dry climate areas. Recently this matter is emerging also in the Czech Republic and in other parts of the temperate and continental climate zone. With progressing climate changes, we can expect that the current water management systems will often have to adapt to new conditions. This paper offers an evaluation of artificial recharge as a drought mitigation method in areas with crystalline bedrock. The core of the study is a pilot location model solution, which provided a tool to assess the efficiency of artificial recharge, operated in order to improve water budged of a shallow hard-rock aquifer. The results of simulations confirmed suitability of artificial recharge through infiltrations wells or ponds, which significantly enhanced water budged of the experimental catchment and improved its potential as a water resource.

Hydrochemical characteristics and evaluation of the granite aquifer in the Alwadeen area, southwest Saudi Arabia

This study was carried out in the Alwadeen area of Khamis Mushayt district of southwestern Saudi Arabia to evaluate the hydrochemical characteristics of the shallow hard rock aquifers. These hard rock aquifers mostly comprise granites and contain significant quantities of groundwater that complement the available groundwater from the unconsolidated alluvial sediments in the nearby wadis. The field investigation indicates two main fracture sets which intersect each other and are oriented in the west-northwest and east-west directions. The granitic rocks in the area are intruded by coarse-grained and quartz-rich monzogranite and pegmatite veins. Hydrogeologically, the fracture systems are important since they facilitate the groundwater storage and assume the transmissive function during times of groundwater abstraction. Given the fact that groundwater in the fractured rock aquifers generally occurs at shallow depths, it may be exposed to contamination from surface and/or near-surface sources, and it is therefore important to evaluate its quality. To this end, a hydrochemical analysis was carried out on six groundwater samples collected from the area. The hydrochemistry revealed that the groundwater is fairly fresh, and facies analysis reveals mixed Na-Cl and Ca-Mg-Cl-SO4 types. Overall, the results reveal that the groundwater is saturated with calcite and dolomite, but unsaturated with gypsum and halite. The degree of salinity increases in the direction of the groundwater flow due to increased rock-water interaction.

An integrated approach to assess the dynamics of a peri-urban watershed influenced by wastewater irrigation

Summary In many urban and peri-urban areas of India, wastewater is under-recognized as a major water resource. Wastewater irrigated agriculture provides direct benefits for the livelihoods and food security of many smallholder farmers. A rapidly urbanizing peri-urban micro-watershed (270 ha) in Hyderabad was assessed over a 10-year period from 2000 to 2010 for changes in land use and associated farming practices, farmer perceptions, socio-economic evaluation, land-use suitability for agriculture and challenges in potential irrigated area development towards wastewater use. This integrated approach showed that the change in the total irrigated area was marginal over the decade, whereas the built-up area within the watershed boundaries doubled and there was a distinct shift in cropping patterns from paddy rice to paragrass and leafy vegetables. Local irrigation supplies were sourced mainly from canal supplies, which accounted for three-quarters of the water used and was largely derived from wastewater. The remainder was groundwater from shallow hard-rock aquifers. Farmer perception was that the high nutrient content of the wastewater was of value, although they were also interested to pay modest amounts for additional pre-treatment. The shift in land use towards paragrass and leafy vegetables was attributed to increased profitability due to the high urban demand. The unutilised scrubland within the watershed has the potential for irrigation development, but the major constraints appear to be unavailability of labour and high land values rather than water availability. The study provides evidence to support the view that the opportunistic use of wastewater and irrigation practices, in general, will continue even under highly evolving peri-urban conditions, to meet the livelihood needs of the poor driven by market demands, as urban sprawl expands into cultivable rural hinterlands. Policy support is needed for enhanced recognition of wastewater for agriculture, with flow-on benefits including improved public health and protection of ecosystem services.

Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

Abstract. While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system-internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure, and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. We analysed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (Environmental Research Observatory ERO AgrHys (ORE AgrHys)). The saturated-zone storage was estimated using distributed shallow groundwater levels and the unsaturated-zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow and saturated, and unsaturated storages led us to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, the integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such a system-like approach is likely to improve model selection.

Assessment of groundwater quality for drinking and irrigation use in shallow hard rock aquifer of Pudunagaram, Palakkad District Kerala

Groundwater samples were collected for pre-monsoon and post-monsoon seasons based on the variation in the geomorphological, geological, and hydrogeological factors for assessment of groundwater quality for drinking and irrigation use in a shallow hard rock aquifer of Pudunagaram area, Palakkad district, Kerala. The samples were analyzed for various physico-chemical parameters and major ion chemistry. Based on analytical results, Gibbs diagram and Wilcox plots were plotted and groundwater quality has been distinguished for drinking and irrigation use. Gibbs diagram shows that the samples are rock dominance and controlling the mechanism for groundwater chemistry in the study area, while Wilcox plot suggest that most of the samples are within the permissible limit of drinking and irrigation use. Further, the suitability of water for irrigation was determined by analyzing sodium adsorption ratio, residual sodium carbonate, sodium percent (%Na), Kelly’s ratio, residual sodium carbonate, soluble sodium percentage, permeability index, and water quality index. It has been concluded that, the water from the study area is good for drinking and irrigation use, apart few samples which are exceeding the limits due to anthropogenic activities and those samples were indisposed for irrigation.

Over‐extraction from shallow bedrock versus deep alluvial aquifers: Reliability versus sustainability considerations for India's groundwater irrigation

The excessive exploitation of groundwater aquifers is emerging as a worldwide problem, but it is nowhere as dramatic and consequential as it is in India, the world's largest consumer, where hundreds of millions of people depend on it. Usually the problem is framed in terms of a long‐term decline in water tables and its consequence for extraction costs, resource depletion, and the sustainability of irrigated agriculture. Here a comparative analysis is provided of coupled groundwater, energy, and irrigation dynamics in two groundwater intensive regions in India that differ in their underlying hydrogeology—the Indian Punjab with its deep alluvial aquifers and the Telangana region in south‐central India with its shallow hard rock aquifers. Using a simple modeling framework and piezometric and agricultural time series, we show that in shallow aquifers the sense in which extraction is excessive is different, and is related to the short‐term reliability of water supply rather than long‐term sustainability. This has important repercussions for irrigated agricultural economies.

Analysis of Shallow Hard Rock Well Pumping and Recovery Test Dataa

ABSTRACTIn this paper equations for calculation of steady, unsteady, confined and unconfined radial ground‐water flow to wells are compared and unified by a single general equation. The validity of the equation is expanded by applying it to a shallow hard rock aquifer where hydraulic conductivity varies with depth. Recommendations are given as to employment of said equation for analysis of pumping and recovery test data of shallow hard rock bore and dug wells.The suggested method for analysis of bore well test data is based on the principle used by Jacob in his method (1950). Drawdown function as function of time is used for graphical analysis of test data. Because of seepage face phenomenon, drawdown measured in water‐table wells must not be used for computation of drawdown function. The function to be computed from drawdown is measured in the aquifer.Hydraulic conductivity is determined from dug well test data as a function of ground‐water inflow into the well discharge which varies during pumping and recovery test because of significant accumulating capacity of the well. Specific yield for the calculation is assumed according to the type of rock, and radius of influence is expressed as a function of time.Derived equations can be used also for hydraulic computation of shallow hard rock water‐table wells.