Changes In Groundwater Discharge Research Articles

Estimation of Streamflow Depletion Caused by Groundwater Withdrawal in the Bokhacheon Watershed in South Korea Using the Modified SWAT Model

Understanding the effects of groundwater withdrawal on streamflow depletion is important for effectively managing water resources. The Soil and Water Assessment Tool (SWAT) model has a groundwater module to calculate the groundwater budget and groundwater discharge. However, the water pumped from the aquifer is not considered in the SWAT module that estimates groundwater discharge. Therefore, this module was modified to consider the impact of groundwater pumping on the changes in groundwater discharge in the Bokhacheon watershed, South Korea. The model’s water transfer module was improved to allow water from the aquifer to be transferred to destination locations, such as residential, industrial, and agricultural lands. Using the modified SWAT, streamflow responses to groundwater extraction were simulated for 2011–2019. The groundwater withdrawal induced decreases of 14.6 and 24.2% in low and drought flows, respectively, at the watershed’s outlet. The groundwater withdrawals decreased groundwater flow and total water yield by 23.5% and 9.8%, respectively, and increased surface flow, lateral flow, percolation, soil water, and evapotranspiration owing to the increased soil moisture resulting from the partial re-infiltration of the groundwater pumped for agricultural irrigation. The modified SWAT can effectively estimate streamflow depletion resulting from groundwater pumping without extensive hydrogeological input data and computational time.

Quantifying climate contributions to changes in groundwater discharge for headwater catchments in a major Australian basin

Groundwater is experiencing a higher risk of aquifer depletion due to longer drought duration and increasing water demand induced by climate change. The climate impacts on groundwater can be propagated to changes in groundwater discharge to rivers, which will deeply alter the connection between groundwater and surface water and reshape the fundamental functions of the river system especially in maintaining environmental flows. In synchronization with the drying and warming climate, groundwater discharges estimated using digital filtering approaches are found to have experienced significant reduction since the 1990s for all our studied headwater catchments in the Murrumbidgee portion of the Murray-Darling Basin. The linkage between precipitation and groundwater discharge is demonstrated to be seasonally dependent. For most of the studied catchments, the dominant precipitation metrics affecting groundwater discharge are the winter precipitation followed by autumn and spring precipitation. Multivariate nonlinear regression modelling suggests that the relationship between groundwater discharge and the dominant climate variables can be represented statistically by a power law. The individual contribution of each dominant climate variable quantified based on the concept of elasticity shows that the decrease in precipitation outweighs the increase in potential evapotranspiration in contributing to the reduction in groundwater discharge. The autumn precipitation accounts for a larger proportion of the changes in groundwater discharge in all studied catchments because of its relatively higher elasticity and change rate. The reduction in groundwater discharge since the mid-late 1990s in the headwater catchments can largely (estimated here at >75%) be attributed to climate factors.

Global Assessment of Current and Future Groundwater Stress With a Focus on Transboundary Aquifers

AbstractWe quantified groundwater stress worldwide by applying the global water resources and water use model WaterGAP 2.2b (Water ‐ Global Assessment and Prognosis) for current conditions (1981–2010) as well as for the 2050s under the worst‐case greenhouse gas emissions scenario RCP8.5. To improve global‐scale groundwater stress assessments, we suggest three new water quantity‐related groundwater stress indicators as well as a new way for communicating projected future groundwater stress at the grid‐cell level (~55 × 55 km) and for larger spatial units such as transboundary aquifers (>20,000 km2). The new indicators encompass the ratio of net abstractions from groundwater to groundwater recharge, human‐induced changes in groundwater discharge, and human‐induced groundwater depletion. We compare them to four conventional indicators used in the Transboundary Waters Assessment Programme and show how they can add value to global‐scale studies or are even more suitable for indicating groundwater stress. We assess potentials and limitations of all indicators by addressing their level of process representation, data requirements, uncertainty, and the underlying different concepts of sustainable groundwater use. To support adaptation to climate change, we recommend showing both the ensemble mean and the worst‐case scenario of future groundwater stress that we derived from five climate and two irrigation scenarios. For characterizing groundwater stress in spatial units such as transboundary aquifers, areal fractions where a selected indicator threshold is exceeded should be considered. Finally, hot spots of future groundwater stress should be identified by combining relative changes from current conditions with absolute values of future groundwater stress.

Co-seismic and post-seismic changes in groundwater discharge: first results from the epicentral region of the Central Italy earthquake 2016

Short and mid-term effects of earthquakes on groundwater flow were documented in several studies.The hydrogeological response of groundwater flow systems to earthquakes is very complex and due to significant changes in permeability. Such hydrologic changes may occur even at great distances from the epicentre and their magnitude may be related to the proximity to the earthquake focus.Central Italy has been hit by several large earthquakes since August 2016. With reference to the carbonate aquifers located in the epicentral region, the following short term effects were observed: a significant increase of the spring discharges and the disappearance of several perched springs.The deep-seated fault movements and fluid redistribution may cause water-level fluctuations as well as changes in groundwater discharge and composition. This study describes a preliminary characterization of such processes.

Study of the seasonality and hydrology as drivers of phytoplankton abundance and composition in a shallow estuary, Weeks Bay, Alabama (USA)

Small, shallow estuaries can be highly vulnerable to land use changes, eutrophication and habitat loss but are understudied with respect to their larger counterparts. Where they are monitored, the descriptors of their environmental status are typically chlorophyll a as a proxy for phytoplankton abundance and nutrient concentration as a presumed driver of the phytoplankton community. We present data from a shallow estuary, Weeks Bay, Alabama (USA), that demonstrates that chlorophyll a and nutrient concentrations are inadequate descriptors of ecological state. Weeks Bay had relatively high nutrient concentrations (86–169µM total nitrogen and 1.0–5.2µM total phosphorus) and highly variable chlorophyll a concentrations (2.2–160.5μgL-1). The variability in chlorophyll a was most highly correlated with nutrient levels and river discharge. There was no relationship between chlorophyll a and community composition. Two of three maxima in chlorophyll a (> 100 μgL-1) were caused by non-toxic chlorophytes and diatoms; the third was dominated by potentially toxic raphidophyte Heterosigma akashiwo. The phytoplankton were diverse even at the class level and community composition varied on both annual and inter-annual scales. The best overall descriptor of phytoplankton composition was the annual cycle in temperature, but inter-annual variability was correlated with hydrology. In the winter, dominance by dinoflagellates, including several taxa that form harmful algal blooms, was correlated with low river discharge, low turbidity and high zooplankton numbers, while dominance by diatoms was correlated with high and variable river discharge and high turbidity. In the summer, dominance by cryptophytes versus diatoms was consistent with changes in groundwater discharge. The dominance of harmful algal bloom taxa vs non-toxic ones could not be inferred from chlorophyll a and/or nutrient concentrations.

Quantifying the impacts of vegetation changes on catchment storage‐discharge dynamics using paired‐catchment data

AbstractIt is widely recognized that vegetation changes can significantly affect the local water availability. Methods have been developed to predict the effects of vegetation change on water yield or total streamflow. However, it is still a challenge to predict changes in base flow following vegetation change due to limited understanding of catchment storage‐discharge dynamics. In this study, the power law relationship for describing catchment storage‐discharge dynamics is reformulated to quantify the changes in storage‐discharge relationship resulting from vegetation changes using streamflow data from six paired‐catchment experiments, of which two are deforestation catchments and four are afforestation catchments. Streamflow observations from the paired‐catchment experiments clearly demonstrate that vegetation changes have led to significant changes in catchment storage‐discharge relationships, accounting for about 83–128% of the changes in groundwater discharge in the treated catchments. Deforestation has led to increases in groundwater discharge (or base flow) but afforestation has resulted in decreases in groundwater discharge. Further analysis shows that the contribution of changes in groundwater discharge to the total changes in streamflow varies greatly among experimental catchments ranging from 12% to 80% with a mean of 38 ± 22% (μ ± σ). This study proposed a new method to quantify the effects of vegetation changes on groundwater discharge from catchment storage and will improve our predictability about the impacts of vegetation changes on catchment water yields.

Evaluating the impact of irrigation on surface water – groundwater interaction and stream temperature in an agricultural watershed

Changes in groundwater discharge to streams caused by irrigation practices can influence stream temperature. Observations along two currently flood-irrigated reaches in the 640-square-kilometer upper Smith River watershed, an important agricultural and recreational fishing area in west-central Montana, showed a downstream temperature decrease resulting from groundwater discharge to the stream. A watershed-scale coupled surface water and groundwater flow model was used to examine changes in streamflow, groundwater discharge to the stream and stream temperature resulting from irrigation practices. The upper Smith River watershed was used to develop the model framework including watershed climate, topography, hydrography, vegetation, soil properties and current irrigation practices. Model results were used to compare watershed streamflow, groundwater recharge, and groundwater discharge to the stream for three scenarios: natural, pre-irrigation conditions (PreIrr); current irrigation practices involving mainly stream diversion for flood and sprinkler irrigation (IrrCurrent); and a hypothetical scenario with only groundwater supplying sprinkler irrigation (IrrGW). Irrigation increased groundwater recharge relative to natural PreIrr conditions because not all applied water was removed by crop evapotranspiration. Groundwater storage and groundwater discharge to the stream increased relative to natural PreIrr conditions when the source of irrigation water was mainly stream diversion as in the IrrCurrent scenario. The hypothetical IrrGW scenario, in which groundwater withdrawals were the sole source of irrigation water, resulted in widespread lowering of the water table and associated decreases in groundwater storage and groundwater discharge to the stream. A mixing analysis using model predicted groundwater discharge along the reaches suggests that stream diversion and flood irrigation, represented in the IrrCurrent scenario, has led to cooling of stream temperatures relative to natural PreIrr conditions improving fish thermal habitat. However, the decrease in groundwater discharge in the IrrGW scenario resulting from large-scale groundwater withdrawal for irrigation led to warmer than natural stream temperatures and possible degradation of fish habitat.

Predicting aquifer response time for application in catchment modeling.

It is well established that changes in catchment land use can lead to significant impacts on water resources. Where land-use changes increase evapotranspiration there is a resultant decrease in groundwater recharge, which in turn decreases groundwater discharge to streams. The response time of changes in groundwater discharge to a change in recharge is a key aspect of predicting impacts of land-use change on catchment water yield. Predicting these impacts across the large catchments relevant to water resource planning can require the estimation of groundwater response times from hundreds of aquifers. At this scale, detailed site-specific measured data are often absent, and available spatial data are limited. While numerical models can be applied, there is little advantage if there are no detailed data to parameterize them. Simple analytical methods are useful in this situation, as they allow the variability in groundwater response to be incorporated into catchment hydrological models, with minimal modeling overhead. This paper describes an analytical model which has been developed to capture some of the features of real, sloping aquifer systems. The derived groundwater response timescale can be used to parameterize a groundwater discharge function, allowing groundwater response to be predicted in relation to different broad catchment characteristics at a level of complexity which matches the available data. The results from the analytical model are compared to published field data and numerical model results, and provide an approach with broad application to inform water resource planning in other large, data-scarce catchments.

Dissolved organic matter composition of winter flow in the Yukon River basin: Implications of permafrost thaw and increased groundwater discharge

Groundwater discharge to rivers has increased in recent decades across the circumpolar region and has been attributed to thawing permafrost in arctic and subarctic watersheds. Permafrost‐driven changes in groundwater discharge will alter the flux of dissolved organic carbon (DOC) in rivers, yet little is known about the chemical composition and reactivity of dissolved organic matter (DOM) of groundwater in permafrost settings. Here, we characterize DOM composition of winter flow in 60 rivers and streams of the Yukon River basin to evaluate the biogeochemical consequences of enhanced groundwater discharge associated with permafrost thaw. DOC concentration of winter flow averaged 3.9 ± 0.5 mg C L−1, yet was highly variable across basins (ranging from <1 to >20 mg C L−1). In comparison to the summer‐autumn period, DOM composition of winter flow had lower aromaticity (as indicated by specific ultraviolet absorbance at 254 nm, or SUVA254), lower hydrophobic acid content, and a higher proportion of hydrophilic compounds (HPI). Fluorescence spectroscopy and parallel factor analysis indicated enrichment of protein‐like fluorophores in some, but not all, winter flow samples. The ratio of DOC to dissolved organic nitrogen, an indicator of DOM biodegradability, was positively correlated with SUVA254and negatively correlated with the percentage of protein‐like compounds. Using a simple two‐pool mixing model, we evaluate possible changes in DOM during the summer‐autumn period across a range of conditions reflecting possible increases in groundwater discharge. Across three watersheds, we consistently observed decreases in DOC concentration and SUVA254 and increases in HPI with increasing groundwater discharge. Spatial patterns in DOM composition of winter flow appear to reflect differences in the relative contributions of groundwater from suprapermafrost and subpermafrost aquifers across watersheds. Our findings call for more explicit consideration of DOC loss and stabilization pathways associated with changing subsurface hydrology in watersheds underlain by thawing permafrost.

Changes on groundwater flow and hydrochemistry of the Gran Sasso carbonate aquifer after 2009 L’Aquila earthquake

The earthquake that struck L'Aquila on April 6 2009 (Mw 6.3) directly affected the Gran Sasso aquifer. Co-seismic and post-seismic changes in groundwater discharge and in hydrochemistry, possibly induced by the earthquake, were observed. Spot and monitoring measurements of the spring discharge, of water table level and of the main physico-chemical parameters of spring waters (T, pH, electrical conductivity, major ions and 222Rn) were thus carried out to determine the effects of the L'Aquila earthquake on groundwater at regional and local scale, to be compared with available data collected since the 1990s.Short- and mid-term effects have been observed in the groundwater flow at recharge and discharge areas. The following short term effects have been observed: i) the sudden disappearance of some springs located along the surface trace of the Paganica Fault; ii) an immediate discharge increase of the Gran Sasso highway tunnel drainages (+20%) and of other springs (+10%); iii) a progressive increase of the water table elevation (+1m) at the boundary of theGran Sasso aquifer during the following month; iv) a sudden lowering of the water table in the recharge area. Similar post-seismic effects have been recorded in the following 20 months, when spring discharge and water table remain higher than the pre-seismic ones in discharge zones.A conceptual model of the earthquake consequences on the Gran Sasso aquifer is proposed herein. The short-term hydrologic effects registered immediately after the mainshock have been caused by a pore pressure increase related to elasto-static aquifer deformation.Apart from the contribution of seasonal recharge observed in 2009-10, mid-term effects observed in the 20 months following the mainshock suggest that there was a change in groundwater hydrodynamics.Supplementary groundwater that flows toward aquifer boundaries and springs in discharge areas reflects a possible increase in hydraulic conductivity in the recharge area. This increase is probably related to fracture cleaning and/or dilatancy.Additional monitoring including hydrochemical data allows a refinement of the proposed model. The outcomes of the hydrochemical spot sampling of the pre-seismic (2001-2007), post-seismic (April 2009) and after-seismic (July and September 2009, may 2010) periods, give the following insights: i) post-seismic groundwater of Tempera spring group was more mineralised and richer in 222Rn than the pre-seismic one; ii) transient changes in pH and calcite saturation index involve the whole aquifer, moving from Tempera springs and spreading from the recharge to discharge areas, causing changes in groundwater hydrochemistry; iii) post-seismic gradual return to previous hydrochemical equilibrium.Both hydrodynamic and hydrochemical observation converge towards a non-permanent increase of the bulk hydraulic conductivity in the aquifer portion close to the Paganica Fault (recharge area and local discharge zone). This fact has caused a lowering of the water table and of the calcite saturation index in recharge areas and simultaneously an increase of water table and flow rate in discharge zones.Complete interpretation of both quantitative and hydrochemical data allows to determine the long-term consequences of this earthquake on the groundwater flow of the Gran Sasso carbonate massif.

Late Quaternary paleohydrology of the central Atacama Desert (lat 22°–24°S), Chile

Research Article| March 01, 2002 Late Quaternary paleohydrology of the central Atacama Desert (lat 22°–24°S), Chile Jason A. Rech; Jason A. Rech 1Department of Geosciences and Desert Laboratory, University of Arizona, 1675 West Anklam Road, Tucson, Arizona 85745, USA Search for other works by this author on: GSW Google Scholar Jay Quade; Jay Quade 1Department of Geosciences and Desert Laboratory, University of Arizona, 1675 West Anklam Road, Tucson, Arizona 85745, USA Search for other works by this author on: GSW Google Scholar Julio L. Betancourt Julio L. Betancourt 2U.S. Geological Survey and Desert Laboratory, University of Arizona, 1675 West Anklam Road, Tucson, Arizona 85745, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2002) 114 (3): 334–348. https://doi.org/10.1130/0016-7606(2002)114<0334:LQPOTC>2.0.CO;2 Article history received: 10 Nov 2000 rev-recd: 13 Jun 2001 accepted: 24 Aug 2001 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jason A. Rech, Jay Quade, Julio L. Betancourt; Late Quaternary paleohydrology of the central Atacama Desert (lat 22°–24°S), Chile. GSA Bulletin 2002;; 114 (3): 334–348. doi: https://doi.org/10.1130/0016-7606(2002)114<0334:LQPOTC>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract In northern Chile, precipitation in the High Andes (>3500 m) recharges groundwater systems that flow down the Pacific slope and feed large aquifers in the hyperarid Atacama Desert. Wetlands, which are often found along the base of the Andes, mark locations where the water table intersects the land surface. At these locations, paleo–wetland deposits, which are present as terraces between 3 and 20 m above modern wetlands, record past water-table heights along the Andean front and are used to reconstruct changes in groundwater discharge. Paleo–wetland deposits in the central Atacama Desert (lat 22°–24°S) record an episode (>15.4–9 ka) of high water tables followed by an episode (8–3 ka) of moderately high water tables. Elevated water tables result from increased groundwater discharge and ultimately from enhanced recharge in the Andes. The concordance of results from three separate hydrologic systems suggests that changes in groundwater discharge and recharge are regional and reflect climatic fluctuations. This interpretation is supported by close agreement with other paleoclimatic records in the region. The periods of greater groundwater discharge were separated by episodes (9–8 and 3–0 ka) of significant groundwater lowering and stream incision, implying greatly diminished discharge.The central Atacama and Andes (lat 22°– 24°S) receive precipitation mainly from moist air masses transported from the Amazon Basin by the South American Summer Monsoon (SASM). Increases in groundwater recharge are therefore thought to reflect an increase in the frequency and/or moisture content of SASM air masses crossing the Andes. Fluctuations in SASM precipitation have previously been linked to summer insolation in the Southern Hemisphere. The wettest period in the central Atacama (>15.4–9 ka), however, coincides with a minimum in austral-summer insolation at 10 ka, suggesting that regional summer insolation is not a dominant influence on the SASM. Instead, intensification of the SASM may be linked to extraregional forcings such as the Walker Circulation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.