695 research outputs found
Groundwater Hydrology
The two fields of knowledge âgeologyâ and âhydrologyâ always go hand in hand, often giving rise to the terms âgeohydrologyâ and âhydrogeology.â The importance of the science of water, commonly called âhydrologic science,â is always complemented by the âscience of the interior of the earth.â Whereas hydrology is concerned with the quality and quantity of underground water, its movement, extraction, and recharge, geology talks of the rock matrix and the structure in which this water is contained, stored, and moved around.In recent times, the knowledge of geohydrology or the hydrology of groundwater has gained an impetus many times its original scale; and with that, acquisition, expansion, research, advancement, and dissemination of this knowledge have become more significant. With so many dimensions of geohydrology available for exploration, research, and technological advancement, any work contributing to any dimension of geohydrology and groundwater will find its right place. This compilation of chapters is going to play a very important part in furthering the knowledge of geohydrology and may prove an interesting and useful read for various cross-sections of academia, researchers, engineers, hydrologists, and all categories of water consumers
Validating the KAGIS blackâbox GISâbased model in a Mediterranean karst aquifer: Case of study of Mela aquifer (SE Spain)
Karst Aquifer GISâbased model (KAGIS model) is developed and applied to Mela aquifer, a small karst aquifer located in a Mediterranean region (SE Spain). This model considers different variables, such as precipitation, land use, surface slope and lithology, and their geographical heterogeneity to calculate both, the runâoff coefficients and the fraction of precipitation which contributes to fill the soil water reservoir existing above the aquifer. Evapotranspiration uptakes deplete water, exclusively, from this soil water reservoir and aquifer recharge occurs when water in the soil reservoir exceeds the soil field capacity. The proposed model also obtains variations of the effective porosity in a vertical profile, an intrinsic consequence of the karstification processes. A new proposal from the NashâSutcliffe efficiency index, adapted to arid environments, is presented and employed to evaluate the model's ability to predict the water table oscillations. The uncertainty in the model parameters is determined by the Generalized Likelihood Uncertainty Estimation method. Afterwards, when KAGIS is calibrated, wavelet analysis is applied to the resulting data in order to evaluate the variability in the aquifer behaviour. Wavelet analysis reveals that the rapid hydrogeological response, typical of a wide variety of karst systems, is the prevailing feature of Mela aquifer. This study proves that KAGIS is a useful tool to quantify recharge and discharge rates of karst aquifers and can be effectively applied to develop a proper management of water resources in Mediterranean areas.This research was funded by the Spanish Ministry of Science and Innovation, Projects CGL2013â48802âC3â3âR and CGL2015â69773âC2â1âP; and by the University of Alicante, Projects GRE15â19 and GRE17â12
Impact of Water Scarcity on the Fenhe River Basin and Mitigation Strategies
This study produced a drought map for the Fenhe River basin covering the period from 150 BC to 2012 using regional historical drought records. Based on meteorological and hydrological features, the characteristics and causes of water scarcity in the Fenhe River basin were examined, along with their impact on the national economy and ecological environment. The effects of water scarcity in the basin on the national economy were determined from agricultural, industrial, and domestic perspectives. The impact on aquatic ecosystems was ascertained through an evolution trend analysis of surface water systems, including rivers, wetlands, and slope ecosystems, and subterranean water systems, including groundwater and karst springs. As a result of these analyses, strategies are presented for coping with water scarcity in this basin, including engineering countermeasures, such as the construction of a water network in Shanxi, and the non-engineering approach of groundwater resource preservation. These comprehensive coping strategies are proposed with the aim of assisting the prevention and control of water scarcity in the arid and semi-arid areas of China
Using hydrogeochemical and ecohydrologic responses to understand epikarst process in semi-arid systems, Edwards plateau, Texas, USA
The epikarst is a permeable boundary between surface and subsurface environments and can be conceptualized as the vadose critical zone of epigenic karst systems which have not developed under insoluble cover. From a hydrologic perspective, this boundary is often thought of as being permeable in one direction only (down), but connectivity between the flow paths of water through the epikarst and the root systems of woody plants means that water moves both up and down across the epikarst. However, the dynamics of these flows are complex and highly dependent on variability in the spatial structure of the epikarst, vegetation characteristics, as well as temporal variability in precipitation and evaporative demand. Here we summarize insights gained from working at several sites on the Edwards Plateau of Central Texas, combining isotopic, hydrogeochemical, and ecophysiological methodologies. 1) Dense woodland vegetation at sites with thin to absent soils (0-30 cm) is in part supported by water uptake from the epikarst. 2) However, tree transpiration typically becomes water-limited in dry summers, suggesting that the plant-available fraction of stored water in the epikarst depletes quickly, even when sustained cave drip rates indicate that water is still present in the epikarst. 3) Flow paths for water that feeds cave drips become rapidly disconnected from the evaporation zone of the epikarst and out of reach for plant roots. 4) Deep infiltration and recharge does not occur in these systems without heavy or continuous precipitation that exceeds some threshold value. Thresholds are strongly correlated with antecedent potential evapotranspiration and rainfall, suggesting control by the moisture status of the epikarst evapotranspiration zone. The epikarst and unsaturated zone in this region can be conceptualized as a variably saturated system with storage in fractures, matrix porosity, and in shallow perched aquifers, most of which is inaccessible to the root systems of trees, although woody vegetation may control recharge thresholds.Keywords: hydraulic disconnection, precipitation thresholds, root zone, plant water use, recharge, epikarst storage, barometric pressure.DOI: 10.3986/ac.v42i2-3.67
Storage dynamics, hydrological connectivity and flux ages in a karst catchment : Conceptual modelling using stable isotopes
This research was supported by The UK-China Critical Zone Observatory (CZO) Programme (41571130071), the National Natural Scientific Foundation of China (41571020, 41601013), the National 973 Program of China (2015CB452701), the National Key Research and development Program of China (2016YFC0502602), the Fundamental Research Funds for the Central Universities (2016B04814) and the UK Natural Environment Research Council (NE/N007468/1). In addition, we thank Sylvain Kuppel, the two anonymous reviewers, Thom Bogaard and the editor for their constructive comments which significantly improved the manuscript. The isotope data as well as rainfall and flow measurements used for this paper can be shared after the ending of our project (2019) according to the project executive policy. Anyone who would like to use the data can contact the corresponding author after signing the agreement. The data were obtained through a purchasing agreement for this study. GIS data in this study are available.Peer reviewedPublisher PD
Simulating hydrological and nonpoint source pollution processes in a karst watershed: A variable source area hydrology model evaluation
AbstractAn ecohydrological watershed model can be used to develop an efficient watershed management plan for improving water quality. However, karst geology poses unique challenges in accurately simulating management impacts to both surface and groundwater hydrology. Two versions of the Soil and Water Assessment Tool (SWAT), Regular-SWAT and Topo-SWAT (which incorporates variable source area hydrology), were assessed for their robustness in simulating hydrology of the karstic Spring Creek watershed of Centre County, Pennsylvania, USA. Appropriate representations of surface water â groundwater interactions and of spring recharge â discharge areas were critical for simulating this karst watershed. Both Regular-SWAT and Topo-SWAT described the watershed discharge adequately with daily Nash-Sutcliffe efficiencies (NSE) ranging from 0.77 to 0.79 for calibration and 0.68â0.73 for validation, respectively. Because Topo-SWAT more accurately represented measured daily streamflow, with statistically significant improvement of NSE over Regular-SWAT during validation (p-value=0.05) and, unlike Regular-SWAT, had the capability of spatially mapping recharge/infiltration and runoff generation areas within the watershed, Topo-SWAT was selected to predict nutrient and sediment loads. Total watershed load estimates (518t nitrogen/year, 45t phosphorus/year, and 13600t sediment/year) were within 10% of observed values (â9.2% percent bias for nitrogen, 6.6% for phosphorous, and 5.4% for sediment). Nutrient distributions among transport pathways, such as leaching and overland flow, corresponded with observed values. This study demonstrates that Topo-SWAT can be a valuable tool in future studies of agricultural land management change in karst regions
Review: Karst springs in Shanxi, China
China is one of a few countries in the world where karst is intensively developed and karst water is heavily utilized as water supply sources. Shanxi is such a Province with the largest karst distribution in places in Northern China, where 19 large karst springs and their catchments are identified to provide important sources of the water supply and ecosystem functioning in Shanxi. Over the years, many problems associated with utilization of karst springs in Shanxi cropped out, including the decrease in spring flow, decline of groundwater level, groundwater contamination and pollution, etc., which severely restrict the sustainable utilization of karst water resources in Shanxi
Dissolved carbon in a large variety of lakes across ïŹve limnetic regions in China
Dissolved carbon in lakes play a vital role in the global carbon cycling. The concentration and dynamics of lake dissolved carbon can be inïŹuenced by both the surrounding landscape and a combination of physical, chemical and biological processes within the lakes themselves. From 2009 to 2016, we conducted a large-scale assessment of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in 249 lakes across a diverse range of climatic, geopedologic, topographical and hydrological conditions in ïŹve Chinese limnetic regions: the East Limnetic Region (ELR), the Northeast Limnetic Region (NLR), the Inner Mongolia-Xinjiang Limnetic Region (MXR), the Yungui Limnetic Region (YGR), and the Tibet-Qinghai Limnetic Region (TQR). We found that the density of the organic matter in the soil in the surrounding landscape plays an important role in the DOC and DIC in lake water, as was evidenced by the high DOC and DIC levels in the NLR, where the soil is respectively organically rich. Conditions in the arid and semi-arid environments (i.e. TQR and MXR) have created a number of brackish/saline lakes and here we found that, DOC and DIC levels (median: 21.79 and 93.72 mg/L, respectively) are signiïŹcantly higher than those in the freshwater lakes (median: 5.80 and 29.38 mg/L). It also appears to be the case that the trophic state of freshwater lakes inïŹuences the spatial variation of DOC. This can be seen in the relationships between DOC and trophic state index (TSI) in agriculturally-dominated regions such as the ELR (R2 = 0.59, p < 0.01), NLR (R2 = 0.65, p < 0.001), and YGR (R2 = 0.78, p < 0.001). Additionally, a close relationship between DOC and DIC can be found in lake waters with diïŹerent trophic states (eutrophic: slp = 0.63, R2= 0.69; mesotrophic: slp = 1.03, R2 = 0.65; oligotrophic: slp = 1.00, R2 = 0.64). This indicates that human activities inïŹuence the quantity and quality of dissolved carbon in inland water across China. This study is able to provide insights regarding the potential eïŹects of climate change and changes in land-use upon the amount of dissolved carbon in lake water
Runoff characteristics and the influence of land cover in drylands of western Texas
In dryland regions, where water is a limited resource, land use/land cover
has undergone and continues to undergo significant change mainly due to
human activities. The nature of runoff from dryland regions and the influence of
land use/land cover change are largely not quantified. The objective of this study
is to examine runoff dynamics and the influence of land cover in drylands of
western Texas across multiple spatial and temporal scales. The study consists
of four major components: (1) an experimental study at Honey Creek upland
catchment (19 ha) to assess vegetation treatment effects on runoff by
hydrometric and isotopic methods; (2) a hydrochemical evaluation of hydrologic
linkage between the upland and bottomland at the second-order Honey Creek
watershed; (3) a detailed precipitation-streamflow analysis at North Concho
River basin to assess long-term and large-scale precipitation-streamflowvegetation
dynamics; and (4) a comparison of streamflow in North, Middle, and
South Concho River basins and a regional streamflow trend analysis for the
entire western Texas. The study indicates runoff production in the drylands of western Texas is dominated by a few large runoff-producing events. The small
catchment experiment indicated that runoff increased about 40 mm per year
when 60% of woody plants were removed. This effect may relate to the
presence of a baseflow component, but was not verified in regional trend
analysis for the Edwards Plateau region where most rivers are spring-fed. The
decrease in streamflow in North Concho River basin after the 1950's is in large
part related to the enhanced infiltration capacity from reduced grazing pressure
and improved vegetation cover. Regional streamflow trend analysis suggests
some headwater areas outside the Edwards Plateau region experienced
patterns of streamflow change similar to those in North Concho River basin,
although artificial impoundments complicated the analysis. The study has
broader application in ecohydrological research beyond specific geographic
areas and specific vegetation types when evaluating the impact of ecosystem
structure change on hydrology and water resources
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