Groundwater Quantity Research Articles

Large-scale permafrost degradation as a primary factor in Larix sibirica forest dieback in the Khentii massif, northern Mongolia

The objective of this study is to investigate the potential causes of widespread Larix sibirica Ledeb. mortality observed in the Khentii massif of northern Mongolia. The ratio of deadwood to living trees in affected stands in the Goricho region, the southernmost study site situated close to the Gobi Desert, was as high as 3.6:1. Moisture fluctuations monitored over 2 years using electrical impedance spectrometry revealed that the Goricho study site had higher soil moisture levels than the two less affected sites Barun Bayan and Dzun Bayan. High soil moisture was recorded in an area characterized by highly skeletal soils, ones with more than 35% by volume of rock fragments, and comparatively shallow soil horizons, from valley to mountains. The layer of permafrost influencing hydrogeological processes is much deeper in the Goricho region compared to the undisturbed study sites. Redundancy analysis confirmed a significant number of dead L. sibirica on sites with developed soils. Live forest stands, however damaged, grow in this region on well-drained scree slopes or on rocky bastions. The mass mortality observed for L. sibirica may be directly linked to accelerated permafrost thaw in the area bordered by the Tuul and the Terelj Rivers. Our assumption is that L. sibirica root system necrosis occurred as a result of long-term waterlogging of developed soils with high spatial heterogeneity, normally able to absorb high quantities of groundwater. The areas unaffected were scree fields and rocky bastions characterized by adequate drainage. All of our findings support the primary stages of large-scale permafrost thaw, i.e., correlating increases in soil moisture with increasing permafrost active layer thickness.

Effect of litter on soil respiration in a man-made Populus L. forest in a dune-meadow transitional region in China’s Horqin sandy land

Human disturbance and climate change both influence the input quantity of plant litter, significantly affecting soil respiration (Rs). However, what leads to a change of relationship between Rs in on-litter input (Rs(NL)) and natural litter input (Rs(CL)) is not yet fully understood. This study selected a man-made Populus forest in a dune-meadow transitional region to observe Rs(NL) and Rs(CL), soil temperature and soil moisture at a depth of 0–10 cm, groundwater depth between April and October in 2014 and 2015, and diurnal variations were carried out during the early, middle, and late stages of the growing seasons. Complex Rs diurnal patterns were observed in different growth stages. The soil moisture beyond field capacity inhibited root respiration and soil microbial activities, thus making Rs(NL) smaller than Rs(CL). When soil moisture was below field capacity with the increase of groundwater depth, dry air and low litter moisture content resulted in the shielding effect of the litter on Rs beyond its decomposition, thus making Rs(NL) consistently larger than Rs(CL). The temperature sensitivity was significantly affected by soil moisture. These results indicate that interactions among the quantity of litter, soil temperature, soil moisture and groundwater, which cause diurnal variations in Rs were diverse. Negative litter respiration may not be a measurement error, but caused by soil moisture which changes the relationship between Rs(NL) and Rs(CL). Thus, this study shows that plant litter has a significant influence on Rs in the dune-meadow transitional region. The findings of this study will provide useful information to understand these fragile ecosystems and the terrestrial carbon cycle.

Water for the millions: Focus Saudi Arabia

Food security is essential for any country. Due to the lack of water resources, countries rely on food imports to satisfy the needs of millions. Oil rich countries, like Saudi Arabia, imports agricultural products for the same reason. This is a short-term solution to circumvent the issue of water scarcity and in future such policy will push the country to desperation. Saudi Arabia withdraws 20 billion m3 of groundwater per year, while the annual recharge of groundwater is only 2.4 billion m3. This additional quantity of groundwater is extracted from non-renewable (fossil) groundwater from trans-boundary Saq-Ram sandstone aquifer of Mesozoic age, with a proven reserve of 103,360 MCM. An amount of about 394 MCM/y flows out of the country. The current 17,300 km2 of irrigated area will shrink in future due to water shortage, thus reducing the GDP contribution below 3%. The best option is to harness geothermal energy to operate the desalination plants. Saudi Arabia can generate desalinated water at the rate of 0.03 US$/m3 (without subsidy). Saudi Arabia cannot afford to overlook this option.

Numerical modeling of seawater intrusion in karstic aquifer, Northwestern Coast of Egypt

The growing population and increasing of the urbanization activities at the Egyptian coastal areas create a great demand on groundwater. El Negila which is located on the Northwestern coast of Egypt is of great environmental, economic, and social importance, so the sustainable management and preservation of the groundwater quantity and quality is imperative. Such task can be addressed through modeling tools that take into account both the human impacts and the effects of climate changes on the hydrogeological system. A variable-density flow model (SEAWAT) had been used to investigate the extent of the seawater intrusion the study area, and to introduce an effective management policy for sustainable development of the groundwater system. An attempt had been made for model calibration; based on adjusting the hydraulic head of the hydrogeological system with respect to the lineaments frequency in the study area. The calibrated numerical model showed the limited extent of the seawater intrusion in the study area under current recharge and abstraction conditions, in addition to that, the model was validated using hydrochemical and stable isotopic data. The aquifer response to different stressing pumping scenario has been tested and predicted up to the year 2022. Furthermore, the impact of rising the seawater level as a result of rapid climatic change was assessed, with pumping stress of the second scenario. It was concluded that the tableland area acts as recharge source and providing an opportunity of recharging the karstic aquifer in the study area especially through the lineaments. The extent of seawater intrusion in the study area for the karstic aquifer is limited, and would increase under the induced activities of pumping as well as seawater rise conditions. A range of withdrawal rate from the study area was recommended to avoid more invasions from seawater.

Quantifying dual recharge mechanisms in deep unsaturated zone of Chinese Loess Plateau using stable isotopes

Apportioning recharge to piston flow and preferential flow is critical for groundwater resource management and hydrologic connectivity evaluation, but the occurrence of the two flows in thick unsaturated zones is still poorly understood. The main objective of this study was to quantify the relative contributions of these two flows in the deep unsaturated zone of the Loess Plateau, China (CLP). The Bayesian mixing model (MixSIAR) was integrated with the line conditioned excess (lc-excess) of stable isotopes (δ2H and δ18O) in precipitation, soil water (8–25 m), and groundwater to determinate the contributions. Piston flow contributed 62 ± 8% to the total recharge while preferential flow did only 38 ± 8%, indicating piston flow was the dominant groundwater recharge mechanism. On comparison with results from similar study sites in the CLP, the primary groundwater recharge mechanism differed among sites and may depend on spatial scales or geomorphology. The information is critical for understanding hydrological process and evaluating groundwater quantity and quality in the highlands of the CLP and other regions with similar hydrogeological conditions.

The role of geological structures on groundwater occurrence and flow in crystalline basement aquifers: a status review

The paper is review on the role of geological structures on groundwater occurrence and flow in Crystalline Basement aquifers. The aim was to study the existing available literatures in order to evaluate structural/lineaments (faults, joints/fractures, folds, shear zone etc.) their influences and controls of groundwater occurrence and flow of bedrock of crystalline rocks of igneous and/or metamorphic origin. Groundwater in the basement aquifers resides/occurs within the weathered overburden and fractured bedrocks which originate from rainfall through the process of hydrological cycle. Remote sensing technique uses satellite imagery or aerial photograph to identify linear features on the ground and attempts to relate these lines to geologic structures capable of transmitting and storing large quantities of groundwater. Faults, joints/fractures and folds act as conduit and make rocks excellent aquifers. These features also, served as channels for groundwater movement which may results to an increased in secondary porosity, permeability and therefore, can results as a groundwater prospective/promising zones in crystalline basement rocks. Keywords: Basement Terrain, Groundwater, Lineament, Movement, Occurrence

STUDIES OF GEOLOGICAL CONDITIONS AND THE ASSESSMENT OF AQUIFER PROPERTIES FOR THE MODEL STUDIES OF GROUNDWATER FLOW IN THE GRUDZIĄDZ AREA

The paper presents the results of a preliminary study of geology and hydrogeological conditions of a Grudziądz groundwater intake. The focus of the study was to develop a conceptual model that will be used in further investigation to create a hydrogeological model. In the intake area two multi-aquifer formations have been distinguished: Quaternary and Paleocene-Cretaceous. The Quartenary multi-aquifer formation, which consists of two aquifers separated by poorly permeable rocks, is primary utility. Groundwater in the Paleocene-Cretaceous aquifer has an elevated mineral content, which makes it not usable. The intake is located near Grudziądz and areas of intense farming, which leads to a hazard of anthropopressure, and may have a negative impact on the groundwater quality and quantity. In-office work conducted for the preparation of article included gathering and description of archival data from over 120 years of intake existence. Data from 53 hydrogeological boreholes have been analyzed. In 2017, field work was also conducted, including several measurements of water table in wells and piezometers of the intake. Water samples have also been collected for chemical analyses. An efficiency assessment of some observation wells has been made, establishing their hydrogeological parameters using the PARAMEX method.

Estimation of effective porosity in large-scale groundwater models by combining particle tracking, auto-calibration and <sup>14</sup>C dating

Abstract. Effective porosity plays an important role in contaminant management. However, the effective porosity is often assumed to be constant in space and hence heterogeneity is either neglected or simplified in transport model calibration. Based on a calibrated highly parametrized flow model, a three-dimensional advective transport model (MODPATH) of a 1300 km2 coastal area of southern Denmark and northern Germany is presented. A detailed voxel model represents the highly heterogeneous geological composition of the area. Inverse modelling of advective transport is used to estimate the effective porosity of 7 spatially distributed units based on apparent groundwater ages inferred from 11 14C measurements in Pleistocene and Miocene aquifers, corrected for the effects of diffusion and geochemical reactions. By calibration of the seven effective porosity units, the match between the observed and simulated ages is improved significantly, resulting in a reduction of ME of 99 % and RMS of 82 % compared to a uniform porosity approach. Groundwater ages range from a few hundred years in the Pleistocene to several thousand years in Miocene aquifers. The advective age distributions derived from particle tracking at each sampling well show unimodal (for younger ages) to multimodal (for older ages) shapes and thus reflect the heterogeneity that particles encounter along their travel path. The estimated effective porosity field, with values ranging between 4.3 % in clay and 45 % in sand formations, is used in a direct simulation of distributed mean groundwater ages. Although the absolute ages are affected by various uncertainties, a unique insight into the complex three-dimensional age distribution pattern and potential advance of young contaminated groundwater in the investigated regional aquifer system is provided, highlighting the importance of estimating effective porosity in groundwater transport modelling and the implications for groundwater quantity and quality assessment and management.

Hydrogeochemical characterization and evaluation of groundwater quality in Kangayam taluk, Tirupur district, Tamil Nadu, India, using GIS techniques

The main objective of the present study is to evaluate the hydrogeochemical characteristics of groundwater and its suitability for drinking water supply in Kangayam taluk, Tirupur district, Tamil Nadu, India. To achieve this objective, seventy-eight groundwater samples were collected from the wells spread over the study area during December 2016. The collected groundwater samples were tested in the laboratory for various hydrogeochemical parameters such as hydrogen ion concentration (pH), electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, potassium, chloride, bicarbonate, carbonate, nitrate, sulphate and fluoride. The analytical results were compared with WHO drinking water standards to assess the suitability of groundwater for drinking purposes. To understand the spatial variation of hydrogeochemical parameters over the study area, choropleth (zonation) maps were prepared using geographical information system (GIS). Overall groundwater quality zones were demarcated by overlaying and integrating all the spatial plots using GIS. Three groundwater quality zones such as (1) most desirable, (2) maximum allowable and (3) not permissible were demarcated based on the limits prescribed by the WHO for drinking purposes. This study indicates that 49% of the study area does not possess potable groundwater. About 21% of the area represents "most desirable" category, and the remaining 30% area represents "maximum allowable" category for drinking purposes. The Piper's trilinear diagram indicates that groundwater of this region is Mixed CaMgCl type. As the groundwater quality is poor nearly 49% of the total area, it is necessary to go for treatment before drinking water supply. It is also essential to recharge the aquifer artificially to improve the quantity and quality of groundwater.

Protecting groundwater levels and ecosystems with simple management approaches

Groundwater quantity is often managed using simple tools. The most common are (1) basin or sub-basin scale volumetric allocations, usually based on either historic use or estimates of recharge, (2) trigger-level management which regulates use according to observations of groundwater level, and (3) buffer zones, which control the location of wells, particularly around groundwater-dependent ecosystems (GDEs). The volumetric approach limits the long-term impact of abstraction and provides a stable, secure supply for groundwater users. However, this approach does not consider the spatial distribution of recharge and discharge, and so is poor at protecting GDEs. Buffer zones provide an effective means of limiting the short-term impact of abstraction on GDEs, and can also be used to shift impact from high to low priority GDEs. However, buffer zones mostly delay the impacts of abstraction on groundwater level and flow, and are less effective for managing long-term impacts. Groundwater response triggers aim to directly control groundwater levels, although the success of this approach is highly dependent on the location of the observation well, and the trigger value. This makes its successful implementation extremely difficult. Used alone, none of these approaches will successfully protect the environment. In combination, they can provide reasonable protection for ecosystems and reliability of groundwater supply for users.

Studies on Environmental Geology and Health Hazards with Reference to Fluoride Rich Groundwater of Nalgonda District,Telangana State, India - a Remote Sensing and G.I.S. Approach.

In the area of study the quality and quantity of groundwater are below the normal standards. In this study spatial statistical methods have been used to demarcate highly polluted zones. Especially fluoride concentrated areas in Nalgonda district. Water quality, especially excess of fluoride concentration in groundwater, is a major concern in the study area. Levels of fluoride in groundwater are considerably greater than the permissible limit especially in Nalgonda district which is known for endemic fluorosis, which is caused by intake of high fluoride water is a slow, progressively, crippling malady affecting young and old, poor and rich, rural and urban population. The area under investigation lies in between the longitude 790 0'-79o 30' E and latitude 16o 45'-17o 15' N. In as many as 1122 habitations in Ranga Reddy and Nalgonda districts, fluorosis is prevalent and they have fluoride content in excess of 1.5 mg/l drinking water. One such area where fluoride contamination in groundwater has been known for several years in parts of Nalgonda district of Telangana state. In this district, several thousands of people in various villages are suffering with advanced fluorosis. A number of studies carried out earlier established the extent of fluoride contamination in different villages. However, no attempt was made to study the spatial distribution of various quality parameters including fluoride in the groundwater of this area. With this background this investigation is planned and undertaken. The spatial variability of groundwater G.I.S techniques were presented. The fluoride variation with reference to other quality parameters was brought out. An attempt is being made to summarise and understand the factors that control the groundwater quality variation in the area of study. A detailed study on fluoride occurrence is taken up, mainly to see its relationship with various other parameters and the influence of hydrogeology and lineament pattern on fluoride occurrence.

Muddy Waters: Refining the Way forward for the “Sustainability Science” of Socio-Hydrogeology

The trouble with groundwater is that despite its critical importance to global water supplies, it frequently attracts insufficient management attention relative to more visible surface water sources, irrespective of regional climate, socioeconomic profile, and regulatory environment. To this end, the recently defined sub-discipline of “socio-hydrogeology”, an extension of socio-hydrology, seeks to translate and exchange knowledge with and between non-expert end-users, in addition to involving non-expert opinion and experience in hydrogeological investigations, thus emphasising a “bottom-up” methodology. It is widely acknowledged that issues pertaining to groundwater quality, groundwater quantity, climate change, and a poor general awareness and understanding of groundwater occurrence and movement are global in their scope. Moreover, while effective communication and engagement represent the key tenet of socio-hydrogeology, the authors consider that multiple actors should be identified and incorporated using stakeholder network analysis and may include policymakers, media and communications experts, mobile technology developers, and social scientists, to appropriately convey demographically focused bi-directional information, with the hydrogeological community representing the communication keystone. Accordingly, this article aims to highlight past and current work, elucidate key areas of development within socio-hydrogeology, and offer recommendations to ensure global efficacy of this increasingly important and growing field going forward. The authors seek to assist in protecting our global groundwater resource for future generations via an improved framework for understanding the interaction between communities and hydrogeological systems.

Groundwater origin, flow regime and geochemical evolution in arid endorheic watersheds: a case study from the Qaidam Basin, northwestern China

Abstract. Groundwater origin, flow and geochemical evolution in the Golmud River watershed of the Qaidam Basin was assessed using hydrogeochemical, isotopic and numerical approaches. The stable isotopic results show groundwater in the basin originates from precipitation and meltwater in the mountainous areas of the Tibetan Plateau. Modern water was found in the alluvial fan and shallow aquifers of the loess plain. Deep confined groundwater was recharged by paleowater during the late Pleistocene and Holocene under a cold climate. Groundwater in the low-lying depression of the central basin is composed of paleobrines migrated from the western part of the basin due to tectonic uplift in the geological past. Groundwater chemistry is controlled by mineral dissolution (halite, gypsum, anhydrite, mirabilite), silicate weathering, cation exchange, evaporation and mineral precipitation (halite, gypsum, anhydrite, aragonite, calcite, dolomite) and varies from fresh to brine with the water types evolving from HCO3 ⋅ Cl-Ca ⋅ Mg ⋅ Na to Cl-Na, Cl-K-Na and Cl-Mg type along the flow path. Groundwater flow patterns are closely related to stratigraphic control and lithological distribution. Three hierarchical groundwater flow systems, namely local, intermediate and regional, were identified using numerical modeling. The quantity of water discharge from these three systems accounts for approximately 83 %, 14 % and 3 %, respectively, of the total groundwater quantity of the watershed. This study can enhance the understanding of groundwater origin, circulation and evolution in the Qaidam Basin as well as other arid endorheic watersheds in northwestern China and elsewhere worldwide.

Conservation of Ground Water at Maheshtala Bleaching and Dyeing Cluster, a Populated Area in West Bengal, India by Implementing Ultra filtration and Reverse Osmosis Based Effluent Treatment Plant—A Case Study

The present study endeavors to assess the quantity and nature of effluents generated from textile bleaching and dyeing units in Maheshtala cluster, West Bengal, India and to provide a treatment process to conserve groundwater resources. Installation of decentralized common effluent treatment plants (CETP) with advanced membrane based treatment system will save ground water which can be reused. Effluent discharged from medium, small and tiny units of this cluster estimated at 20,000 KLD lifted through pumps from groundwater aquifer. Studies in Kalikapur area under Maheshtala cluster during 2012–2016 showed following mean concentrations of various physico-chemical variables: pH (7.29), BOD (150 mg/l), COD (457 mg/l), TDS (3534 mg/l), TSS (108 mg/l)) and metals such as Cd (0.02 mg/l), Pb (0.20 mg/l), Cr (0.21 mg/l), Fe (1.69 mg/l) and Na (2367 mg/l). These values exceeded the standard permissible limits stipulated by IS: 10500 (2012) and WHO (2003). Due to absence of CETPs in the cluster wastewater laden with toxic trace metals affects the environment and human health, degrades the quantity and quality of both surface and groundwater, contaminates agricultural land, crops, fruits and vegetables, and causes harm to aquatic life forms. Four to five decentralized CETPs are required to install at different locations of the Mahestala region with a capacity of 5000 KLD each, at least one in Kalikapur area, to purify large volume of wastewater (20,000 KLD) and to produce reusable groundwater to an extent of 11,000 KLD (55%) in a populated urban area at Maheshtala near Calcutta, a leading city of India. Further, population and textile bleaching and dyeing industries in last 10 years are increasing. The reuse of wastewater is inevitable as rainfall is decreasing in last 10 years and a result the groundwater recharge is also decreasing as per West Bengal Statistical Handbook 2014.

Management of Groundwater Quality and Quantity: Gediz River Basin Pilot Study

This study provided methods and methodologies in compliance with the national legislations that will ensure proper management of groundwater in terms of both quality and quantity. The methodologies developed in this manner were implemented in the Gediz River Basin in Turkey. A total of 76 groundwater bodies delineated in the Basin were subjected to characterization, where the anthropogenic pressures on the quality and quantity of groundwater and their possible impacts were determined. Detailed risk analysis done by the available data revealed to the groundwater bodies which were under risk of achieving good status in terms of quality and/or quantity. In order to disclose the current status of all groundwater bodies, in-depth analyses (establishing threshold values, comparison of the measured values to the threshold values/quality standards, water budget calculations, etc.) were performed and supported by the comprehensive field investigations and monitoring. Ultimate results indicated that 33 groundwater bodies out of 76 were in poor status; and hence, all these bodies should be included in the programme of measures. Moreover, all the monitoring points at which the threshold values and/or quality standards are exceeded were also included in the programme of measures. Finally, the required measures to be taken in the Gediz River Basin at different scales (basin, groundwater body and monitoring point); to improve the poor status or to conserve the good status of groundwater, were pointed out considering both its quality and quantity.

Rooting depth controls potential groundwater recharge on hillslopes

Land use changes may modify ecohydrological processes in soil, altering groundwater quantity and quality in arid and semi-arid regions. The effects of land use change were well documented on flatlands, but the effect of rooting depth on groundwater recharge is poorly understood. This study is to evaluate how conversion of shallow-rooted to deep-rooted vegetation affects groundwater recharge at different landscape positions (i.e. tableland, upslope, midslope, and downslope). Two adjacent transects were selected for a paired plot design: one was covered with shallow-rooted perennial grasses and the other was planted with deep-rooted apple trees or apricot trees in 1990s. Soil cores (as deep as 13–25 m) were collected at each of the four landscape positions along the two transects for the determination of soil water contents, root distributions, and soil tritium contents. Groundwater recharge rates beneath shallow-rooted vegetation were determined from the tritium peak method, and that beneath deep-rooted vegetation were calculated by subtracting the annual soil water deficit from recharge rates beneath shallow-rooted vegetation. Results show that, there is no significant difference in groundwater recharge between the four landscape positions under shallow-rooted vegetation (p > 0.05); however, there is a substantial difference between different slope positions along the other transect (p < 0.05). Cross comparison between the two transects show that conversion from the shallow-rooted to deep-rooted vegetation resulted in a significant reduction of groundwater recharge (p < 0.05) which reduced to virtually zero when the rooting depth is deeper than 15 m. Therefore, we conclude that rooting depth is a major control of groundwater recharge. This study is the first attempt to evaluate the effect of deep-rooted vegetation in the deep unsaturated zone on groundwater recharge on hillslopes with terraces, having important implications to afforestation and to understanding ecohydrological processes in natural ecosystems.

Evaluating the groundwater resource potential of the Dundas buried bedrock valley, southwestern Ontario: an integrated geological and hydrogeological case study

Population growth in the groundwater-dependent municipalities of southwestern Ontario has prompted interest in the exploration for new, previously untapped, groundwater resources. In this study, the groundwater resource potential of the sediments infilling a deeply buried bedrock valley network centred beneath the Region of Waterloo and the counties of Brant and Hamilton–Wentworth are explored. The objectives of this study are to further refine valley location and geometry, understand infilling sediments and their hydrogeological properties, and characterize waters contained within the aquifers to inform future water management decisions. Results of a regional ground gravity survey were instrumental in locating buried bedrock valleys and guided follow-up drilling. Continuous sediment coring and monitoring well installations were completed to target thick and coarse-grained sediment packages that, based on existing borehole data, showed aquifer potential. Hydraulic testing and groundwater sampling results provided valuable insights into groundwater quantity and quality. Highly transmissive aquifers, some worth investigating further, have been identified within portions of the valley network. The aquifers appear to occur at a number of stratigraphic positions and do not necessarily occur as the deepest unit overlying bedrock. Bedrock topography likely played a role, however, in their preferential preservation. They are commonly overlain by thick sequences of relatively impermeable sediments, providing excellent protection from anthropogenic contamination. Information from water chemistry, however, does suggest hydraulic connection to the surface at some locations. Groundwater quality and quantity information combined with a conceptual three-dimensional geologic model aids in the selection of groundwater resource exploration targets within the untapped resources of the deep, Dundas buried valley sediments.

Long term groundwater balance and water quality monitoring in the eastern plains of Urmia Lake, Iran: A novel GIS based low cost approach

Groundwater quality and quantity are two major challenges in arid and semi-arid regions, due to their critical roles in sustainable agricultural development. Irrigated lands are spread all over Urmia Lake's surrounding plains in Iran. Due to the risk of saltwater intrusion as a result of over-exploitation from groundwater resources, it is important to monitor the groundwater quality and quantity through time and space. In this paper, the groundwater quantity was assessed over 11 years applying a novel groundwater balance estimation method based on water table data and 3D modeling; groundwater quality were monitored over 10 years using GIS and geostatistics; and the saltwater intrusion were investigated through generated quality maps and regression analysis. Results indicate that the groundwater balance was negative during the study period. Furthermore, the aquifers quality decreased over the study period, which was severe in west and southwest of the study area. The saltwater intrusion was proved and salty water was spread from west to other zones. The saltwater intrusion into aquifers increased electrical conductivity, chloride and sodium concentrations and will cause many ecological and agricultural problems. The novel and practicable approach utilized for groundwater balance quantitative assessment is suitable for countries lacking hydrological properties databases.

Hydrogeochemical characterization of a shallow alluvial aquifer: 1 baseline for groundwater quality assessment and resource management

Considering the progressive depletion of groundwater quantity and the alteration of superficial and groundwater quality in the Madrid region, a highly populated area with extended urbanizations in the north and agricultural activities in the south, we conducted a monitoring study over a period of 2.5 years (2015–2017). The study was conducted in the Jarama-Tajuña shallow alluvial aquifer system located southeast of Madrid, where the exploitation of the aquifer and the Jarama river have increased exponentially in the last decade being affected by both urban and agricultural activities. Our aims were to provide: i) a geochemical characterization of the surface and groundwater properties; ii) identify the process responsible for the geochemical evolution and mineralization of the waters; iii) assess the water quality (i.e. nitrates, ammonia, sodium and chloride as potential contaminants) and the water suitability for irrigation (SAR, Wilcox, KI and MH indexes); and iv) identify the main sources of contamination in the area.A set of plots, ion ratios, correlation coefficients, multivariate statistical analyses and indexes were performed. Results indicated that rock weathering largely controls the hydrogeochemistry of the system and that wastewater treatment plant discharges and agricultural practices significantly affect the composition of the water, causing an important decline of both surface and groundwater chemical quality. Nonetheless, water suitability for irrigation is admissible. Thus, taking additional measures to increase its quality are not necessary.With this study we aimed to establish a base line to evaluate future changes in the groundwater properties from the Madrid region enabling the planners and policy makers to develop a strategy to mitigate the impact of the exponential increase of urban and agriculture activities on groundwater resources.

Large-scale association analysis of climate drought and decline in groundwater quantity using Gaussian process classification (case study: 609 study area of Iran).

BackgroundThe level of groundwater resources is changing rapidly and this requires the discovery of newer groundwater resources. Drought is one of the most significant natural phenomena affecting different aspects of human life and environment. During the last decades, the application of artificial intelligent techniques has been recognized as effective approaches to forecast an annual precipitation rate.MethodIn this study, the association analysis of climate drought and a decline in groundwater level is addressed using Gaussian process classification (GPC) and backpropagation (BP) artificial neural network (ANN). This methodology is proposed to create a framework for decision making and reduce uncertainty in water resource management calculations, and in particular to optimize the management of groundwater drinking water sources.ResultsUnderground water levels in 609 study plains in Iran were used to predict drought over the test period, extending from 2017 to 2021. The artificial intelligence methods were implemented in the Python programming environment to achieve an annual precipitation rate. A statistical summary of the Rasterized Cells of the zoning maps was used to validate the prediction results. Considering the relationship between water quality reductions and drought in Iranian aquifers due to the occurrence of groundwater drought periods, the results were validated by analysis of the effect of climate drought using the Standardized Precipitation Index (SPI) on the occurrence of observed droughts with the Groundwater Resources Index (GRI). The results are well-illustrated by the observation of the predicted digits in the third dimension of the Gaussian distribution.ConclusionAccording to the SPI indicator, the southern regions of the country, and especially the central parts of the plain, can be considered the most affected areas by the most severe future droughts. The prediction results indicate a decrease in drought severity as part of a two-year sequence involving a recurrence of drought exacerbation and relative decline, as well as a failed state after the critical condition of aquifers.