Trends In Groundwater Quality Research Articles

Exploring Groundwater Quality Trends in Valliyar Sub-Basin, Kanniyakumari District, India through Advanced Machine Learning Techniques

Exploring Groundwater Quality Trends in Valliyar Sub-Basin, Kanniyakumari District, India through Advanced Machine Learning Techniques

Prediction of ground water quality in western regions of Tamilnadu using LSTM network

Assessing and safeguarding groundwater quality is critical for sustaining life in water-scarce regions like western Tamil Nadu. The motivation behind this study stems from the pressing need to address water quality challenges in a region grappling with scarcity. Despite existing efforts, a notable research gap exists in predictive tools that comprehensively capture the nuanced temporal variations and trends in groundwater quality. This is where the LSTM network steps in, showcasing exceptional accuracy in short-term predictions and discerning long-term trends. This research uses Long Short-Term Memory (LSTM) networks, a variant of recurrent neural networks, to predict groundwater quality in South Indian Regions, especially in Tamil Nadu. Extensive data, encompassing parameters such as pH, dissolved oxygen, turbidity, and various chemical constituents, were gathered over an extended timeframe. The LSTM model was then trained on this historical dataset, factoring in temporal dependencies and seasonality inherent in groundwater quality data. The validation process rigorously tests the LSTM model against actual groundwater quality measurements. The results were impressive, as the model demonstrated a remarkable ability to unravel the complex variations in groundwater quality.

Utilizing geographic information system and indexing to evaluate irrigation suitability of groundwater in Kalihati Upazila, Bangladesh

The aim of this research was to evaluate groundwater quality for irrigation in Kalihati Upazila, Bangladesh, a region that is significantly reliant on groundwater for crop development, especially during dry periods. By combining hydrochemical analysis and Geographic Information System (GIS), the research examined the physicochemical attributes and their spatial distribution. Fifteen groundwater samples from various locations were analyzed to measure parameters such as sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium adsorption ratio (MAR), electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), Kelly's ratio (KR), permeability index (PI), and potential salinity (PS). The pH of the groundwater ranged between 5.51 and 7.53, indicating slightly acidic to moderately alkaline conditions suited for irrigation. The EC ranged between 115.7 and 458 μS/cm, mostly falling into the "excellent" or "good" categories. Groundwater displayed irrigation suitability with TDS below 182 ppm and low SAR values, but variable RSC and MAR values indicated localized water quality issues. Based on the irrigation water quality index, all samples were within the "permissible" range. However, GIS-generated maps showed disparities in groundwater quality across the study area. Correlation matrices revealed significant links between various factors. Both the Piper and Gibbs diagrams displayed a prevalent Ca-HCO3 groundwater type influenced by geological formations. Overall, the study confirmed groundwater's appropriateness for irrigation while recommending periodic evaluations due to a few uncertainties. In conclusion, the study found that hydrochemical analysis, GIS mapping, and correlation matrices reveal groundwater quality and spatial trends, allowing for sustainable water resource management and agricultural advancement.

Hydrogeochemical changes during artificial groundwater well recharge

Artificial groundwater recharge is a relatively economic and efficient method for solving shortages and uneven spatial-temporal distribution of water resources. Changes in groundwater quality during the recharge process are a key issue that must be addressed. Identifying the hydrogeochemical reactions that occur during recharge can be vital in predicting trends in groundwater quality. However, there are few studies on the evolution of groundwater quality during artificial recharge that comprehensively consider environmental, chemical, organic matter, and microbiological indicators. Based on an artificial groundwater recharge experiment in Xiong'an New Area, this study investigated the hydrogeochemical changes during groundwater recharge through a well. The results indicate that (1) as large amounts of recharge water (RW) were injected, the groundwater level initially rose rapidly, then fluctuated slowly, and finally rose again. (2) Water quality indicators, dissolved organic matter (DOM), and microbial communities were influenced by the mixture of RW and the background groundwater before recharge (BGBR), as well as by water-rock interactions, such as mineral dissolution-precipitation and redox reactions. (3) During well recharge, aerobic respiration, nitrification, denitrification, high-valence manganese (Mn) and iron (Fe) minerals reduction dissolution, and Mn2+ and Fe2+ oxidation-precipitation occurred sequentially. (4) DOM analysis showed that protein-like substances in the BGBR were the main carbon sources for aerobic respiration and denitrification, while humic-like substances carried by the RW significantly enhanced Mn and Fe minerals reduction dissolution. Therefore, RW quality significantly affects groundwater quality after artificial groundwater well recharge. Controlling indicators, such as dissolved oxygen (DO) and DOM, in the RW can effectively reduce harm to groundwater quality after recharge. This study is of theoretical and practical significance for in-depth analysis of the evolution of groundwater quality during artificial well recharge, prediction of trends in groundwater quality during and after recharge and ensuring groundwater quality safety.

Impact of mine closure on groundwater resource: Experience from Westrand Basin-South Africa

The mining sector is at the edge of expanding to cater for natural resources that are much needed for technological development and manufacturing. Mushrooming of mines will consequently increase the number of mines closure. Moreover, mines closure have adverse impact on the environment at large and specifically on water resources. This study analyses historical groundwater quality parameters in mine intensive basin of Westrand Basin (WRB) to understand the status of groundwater quality in relation to mining activities and mine closure. Geographic information system (GIS) was used to map the spatio-temporal variation of groundwater quality in the basin and groundwater quality index (GQI) to evaluate its status. The coefficient of variation (CV) was applied to understand the stability of groundwater quality after the mine closure. Results indicated unstable and altered trend with increasing levels of acidity and salts concentration around the mines vicinity following the mine closure. The resultant maps indicated a significant deterioration of groundwater quality around the WRB with concentrations decreasing downstream. Obtained average GQI for the study period of 1996–2015 suggested a moderate groundwater quality at a range of GQI = 64–73. The CV indicated varying water quality at CV > 30% suggesting presence of source of contamination. Observed groundwater quality trends in Westrand basin suggested that mines closure present potential threat on groundwater quality and thus, a need for a robust mine closure plan and implementation.

Groundwater Quality Assessment Using Multi-Criteria GIS Modeling in Drylands: A Case Study at El-Farafra Oasis, Egyptian Western Desert

The most critical issue that was the main research interest is its groundwater quality which is vital for public health concerns. Groundwater is a significant worldwide water supply for diverse communities, especially in dryland regions. Groundwater quality assessment in desert systems is largely hindered by the lack of hydrological data and the remote location of desert Oases. This study provides a preliminary understanding of the influences of climate, land usage, and population growth on the groundwater quality in El-Farafra Oasis in the Western Desert in Egypt from 2000 to now. Therefore, the study’s main objective was to determine the extent of change in temporal water quality and the factors causing it. The present study integrates chemical analyses and geospatial modeling better to assess groundwater quality in the study area. A chemical analysis of thirty-one groundwater samples from wells representing each study area was carried out during three time periods (2000, 2010, and 2022). Several chemical properties of groundwater samples gathered from wells in the research area were analyzed. Furthermore, the groundwater quality trend from 2000 to the present was identified using three approaches: Wilcox and Schoeller Diagram in Aq.QA software, interpolation in the ArcGIS software, and Ground Water Quality Index (GWQI). Moreover, the influence of changing land usage on groundwater quality was studied, and it was found that the increase in agriculture and urbanization areas is linked to groundwater quality degradation. The findings revealed that the barren area in 2000, 2010, and 2022 was 371.7, 362.0, and 343.2 km2, respectively, which indicates a substantial decrease of 6.2% within this research timeframe. In contrast, agriculture and human-made structures have expanded by 1.8%. Also, population growth has led to an increase in water consumption as the population has grown at a rate of 7.52% annually from 2000 to 2020. As the climatic condition increases from 2000 to 2022, these changes could extend to the water quality in shallow aquifers with increasing evaporation. Based on the water quality spatial model, it is found that, despite a declining tendency in the rate of precipitation and an expansion in agricultural areas and population growth, the water quality was still appropriate for human and farming consumption in large areas of the study area. The presented approach is applicable to the assessment of groundwater in desert regions in the Middle East area.

Geogenic controls on the high levels of uranium in alluvial aquifers of the Ganga Basin

The Indo-Gangetic Basin (IGB) alluvial aquifer system provides a reliable drinking water supply to over half a billion people. Understanding the groundwater quality, aquifer processes, groundwater storage, and depletion trends in the IGB alluvial aquifer system— one of the world's most important freshwater resources has been the focus of many previous studies. However, understanding what governs uranium variability in the IGB alluvial aquifer system— for example, whether uranium is released from natural deposits or anthropogenic sources such as mill tailing, emissions from the nuclear industry, combustion of fossil fuels, and phosphate fertilizers— are under-explored but critically important for constraining the environmental fate of uranium. Here, we present surface and groundwater uranium concentration data in the central parts of the IGB alluvial aquifer system. We find a high concentration of groundwater uranium above the World Health Organization provisional guideline value of 30 μg/L in 17% (n = 29) of collected groundwater samples, whereas other heavy metals, namely Cr, Ni, Pb, and Cd were within the recommended range. Trace element systematic demonstrates that anomalous uranium enrichment is primarily derived from geogenic sources, while uranium mobility is predominantly controlled by the alkalinity (a proxy for bicarbonate), hence by soluble uranyl carbonate complexes. As in the year 2020, the Bureau of Indian Standard incorporated uranium as a possible drinking water contaminant, our dataset calls for additional assessments of groundwater uranium concentrations in Indian groundwater resources because uranium concentration data are scarce compared to other geogenic contaminants such as arsenic and fluoride. We conclude that uranium, like arsenic and fluoride, is also critical geogenic contaminant in the alluvial aquifers that needs to be better monitored as higher levels of uranium in drinking water have adverse health effects.

Assessment of Groundwater Variability in Mbagathi River Catchment

Groundwater is increasingly an important source of water. Assessment of its variability spatially and temporally besides quality and quantity is not easy. Groundwater contains multiple range of chemical parameters. This contribution proposes a water quality index (WQI) to synthesize various groundwater quality parameters (Na + , F - , Cl ‑ , SO 4 2- , Ca 2+ , Mg 2+ , K + and NO 3 - ) in Geographic Information Systems (GIS) based environment. The parameters are analyzed relative to the Kenya Standard (KS) East Africa Standard (EAS) 12:2018 standard in the Mbagathi river catchment, a metropolitan area, Southwest of Nairobi, Kenya. Prediction maps for three seasons (wet, moderate and dry) and a combination all three seasons were produced. Based on WQI classification, results showed 36% - 28% good, 58% - 61% fair, and 6%-11% poor. A noticeable declining groundwater quality trend from wet to dry seasons was observed. Groundwater quality deterioration was observed to be greater in areas with higher yield and water rest level. Groundwater is safe for drinking, barring the elevated fluoride content in some areas. Application of GIS was a valuable tool in exploration of groundwater characteristics. Maps generated can serve as first-hand information for groundwater development. Keywords : groundwater, quality, kriging, semivariogram, variability DOI: 10.7176/JEES/12-4-03 Publication date: April 30 th 2022

Impact of land use/land cover changes on water quality and human health in district Peshawar Pakistan

The quality and quantity of groundwater resources are affected by landuse/landcover (LULC) dynamics, particularly the increasing urbanization coupled with high household wastewater discharge and decreasing open lands. This study evaluates temporal changes of groundwater quality for 2012 and 2019, its relation to Landuse/landcover, and its impact on Peshawar's residents (study area), Pakistan. A total of 105 and 112 groundwater samples were collected from tube wells in 2012 and 2019. Samples were then analyzed for seven standard water quality parameters (i.e., pH, electric conductivity (EC), turbidity, chloride, calcium, magnesium, and nitrate). Patient data for waterborne diseases were also collected for the years 2012 and 2019 to relate the impact of groundwater quality on human health. Landsat satellite images were classified for the years 2012 and 2019 to observe landuse/landcover dynamics concerning groundwater quality. Results manifested a decrease in groundwater quality for the year 2019 compared to 2012 and were more highlighted in highly populated areas. The nitrate concentration level was found high in the vicinity of agricultural areas due to the excessive use of nitrogenous fertilizers and pesticides, and thus the methemoglobinemia patients ratio increased by 14% (48–62% for the year 2012 and 2019, respectively). Besides, Urinary Tract Infections, Peptic Ulcer, and Dental Caries diseases increased due to the high calcium and magnesium concentration. The overall results indicate that anthropogenic activities were the main driver of Spatio-temporal variability in groundwater quality of the study area. The study could help district health administration understand groundwater quality trends, make appropriate site-specific policies, and formulate future health regulations.

Association of Radionuclide Isotopes with Aquifer Solids in the Midwestern Cambrian–Ordovician Aquifer System

Groundwater, an important source of drinking water globally, is susceptible to contamination by naturally occurring metals and radionuclides. Regional trends in groundwater quality are useful in pr...

Groundwater quality trend and trend reversal assessment in the European Water Framework Directive context: an example with nitrates in Italy

Groundwater resources are of utmost importance in sustaining water related ecosystems, including humans. The long-lasting impacts from anthropogenic activities require early actions, owing to the natural time lag in groundwater formation and renewal. The European Union (EU) policy, within the implementation of the Water Framework Directive (WFD), requires Member States to identify and reverse any significant and sustained upward trend in the concentration of pollutants, defining specific protection measures to be included in the River Basin Management Plans (RBMP). In Italy, official guidelines for trend and trend reversal assessment have been published recently. Statistical methods, such as the Mann-Kendall test for trend analysis and the Sen’s method for estimating concentration scenarios, should be applied at the fixed terms stated by the WFD implementation cycles to identify upward trends, while the Pettitt test is proposed for the identification of trend reversal. In this paper, we present an application of a slightly modified version of the Italian Guidelines to a groundwater body in Northern Italy featuring nitrate pollution and discuss its advantages and limitations. In addition to Pettitt test, for the trend reversal analysis, we apply the Mann-Kendall test in two sections and compare the results. We conclude that this method seems more reliable than Pettitt test to identify a reversal point in quality time series. The overall procedure can be easily applied to any groundwater body defined at risk across Europe, for the assessment of the upward trends of pollutants and their reversal, even with little chemical monitoring data. Although focused on the EU legislative framework, this procedure may be relevant for a wider context, allowing to individuate upward trend as early warning for contamination processes in an integrated water resources management context.

Groundwater Quality Characterization in an Overallocated Semi-Arid Coastal Area Using an Integrated Approach: Case of the Essaouira Basin, Morocco

In this study, hydrogeochemical analyses were combined with geographic information system (GIS) tools to investigate salinization sources of groundwater in the downstream part of the Essaouira basin, and to analyze the spatiotemporal trends in groundwater quality. To assess groundwater suitability for drinking purposes, the quality of sampled water was compared with the World Health Organization (WHO) and the Moroccan guidelines. Wilcox and US salinity laboratory (USSL) diagrams were used to evaluate groundwater suitability for irrigation. Hydrogeochemical analyses revealed that groundwater is of Na-Cl and Ca-Mg-Cl types. The analyses of the correlation between the chemical elements showed that the water–rock interaction and the reverse ion exchange are the major processes impacting groundwater degradation in the study area. The study of groundwater suitability for drinking and irrigation purposes shows that groundwater quality in the study area is permissible, but not desirable for human consumption. Additionally, groundwater is permissible for agricultural use but with high-salinity hazards. The spatial distribution of the physicochemical elements shows a general upward gradient from the north to the south and from the east to the west. The trend in groundwater quality during the last five years shows a shifting in the quality from the mixed Ca-Mg-Cl to the Na-Cl type.

Countrywide Groundwater Quality Trend and Suitability for Use in Key Sectors of Korea

Under changing climate, increasing groundwater use has risen the concern for groundwater quality variations over recent years, to maintain a healthy ecosystem. The objectives were to identify trend of temporal variations in groundwater quality and its suitability for different uses in Republic of Korea. Water quality data were collected from 198 monitoring stations of Groundwater Quality Monitoring Network (GQMN), annually for the period of ten years (2008–2017). Non-parametric trend analysis of a Mann–Kendall test and Theil–Sen’s slope was done on groundwater physico-chemical data of ten years. Groundwater suitability evaluation was done for use in main sectors including domestic (drinking) and agriculture (irrigation). For drinking suitability analysis, results were compared with World Health Organization (WHO) and Korean Ministry of Environment (KME) established guidelines. For irrigation suitability evaluation, electrical conductivity (EC), Sodium Adsorption Ratio (SAR), percent of Na+, Residual Sodium Carbonate (RSC), US Salinity Laboratory (USSL), and Wilcox diagram were used. Most significantly, water type belongs to Ca-HCO3 and Ca-SO4 types, but a small proportion belongs to Na-CO3 and Na-Cl types. Approximately, 96% and 93% of groundwater samples are suitable for drinking, based on WHO and KME guidelines, respectively. Around 98% and 83% of groundwater samples are in suitable range for irrigation use, based on USSL and Wilcox diagrams, respectively.

Identifying areas of degrading and improving groundwater-quality conditions in the State of California, USA, 1974\u20132014

Areas of improving and degrading groundwater-quality conditions in the State of California were assessed using spatial weighting of a new metric for scoring wells based on constituent concentrations and the direction and magnitude of a trend slope (Sen). Individual well scores were aggregated across 2135 equal-area grid cells covering the entire groundwater resource used for public supply in the state. Spatial weighting allows results to be aggregated locally (well or grid cell), regionally (groundwater basin), provincially, or statewide. Results differentiate degrading (increasing concentration trends) areas with low to moderate concentrations (unimpaired) from degrading areas with moderate to high concentrations (impaired). Results also differentiate improving areas (decreasing concentration trends) in the same manner. Multi-year to decadal groundwater-quality trends were computed from periodic, inorganic water-quality data for 38 constituents collected between 1974 and 2014 for compliance monitoring of nearly 13,000 public-supply wells (PSWs) in the State of California. Mann-Kendall (MK) rank correlations and Sen’s slope estimator were used to detect statistically significant trends for the entire period of recorded data (long-term trend), for the period since 2000 (recent trend), for different pumping seasons (seasonal trend), and for reversals of trends. Statewide, the most frequently detected trends since 2000 were for nitrate (36%), gross alpha/uranium (10%), arsenic (14%), total dissolved solids (TDS) (23%), and the major ions that contribute to TDS (19–28%). The Transverse and Selected Peninsular Ranges (TSPR) and the San Joaquin Valley (SJV) hydrogeologic provinces had the largest percentage of areas with moderate to high nitrate concentrations and groundwater quality trends. Improving nitrate concentrations in parts of the TSPR is associated with long-term managed aquifer recharge that has replaced historical, agriculturally affected groundwater with low-nitrate recharge in parts of the TSPR. This example suggests that application of dilute, excess surface water to agricultural fields during the winter could improve groundwater-quality in the SJV over the long term.

Groundwater pollution early warning based on QTR model for regional risk management: A case study in Luoyang city, China

Groundwater pollution early warning has been regarded as an effective tool for regional groundwater pollution prevention, especially in China. In this study, the systemic model was established to assess the groundwater pollution early warning by integrating the present situation of groundwater quality (Q), groundwater quality trend (T) and groundwater pollution risk (R). The model integrated spatial and temporal variation of groundwater quality, and combined the state and process of the groundwater pollution. Q, T and R were assessed by the methods of fuzzy comprehensive assessment, Spearman or nonparametric Mann-Kendall trend test, and overlay index, respectively. Taking the Luoyang City as an example, the groundwater pollution early warning mapping was generated, and verified by corresponding the groundwater quality classes and the early warning degrees. The results showed that the groundwater was dominated by the levels of no warning and light warning, which accounted for 77% of the study area. The serious and tremendous warning areas were affected by the worse trend and relatively bad/bad present situations of groundwater quality with the typical contaminants of total hardness, nitrate, Hg and COD. In summary, the present situation of groundwater quality was the most important factor of groundwater pollution early warning mapping in the study area. The worse trend of groundwater quality played equally a key role in the local regions, as well as the high pollution risk, which was mainly affected by the pollution source loading. Targeted measures for groundwater pollution prevention were proposed in the corresponding degrees of groundwater pollution early warning. The QTR model was proved to be effective for assessing the regional groundwater pollution early warning. The accuracy of the model could be improved if there is further data acquisition of groundwater quality in longer time series and in larger number, and further investigation of pollution sources.The QTR model is proposed and proved to be effective for assessing regional groundwater pollution early warning.

Climate Change Impacts on Groundwater Resources in the Coastal Karstic Adriatic Area: A Case Study from the Dinaric Karst

The Bokanjac–Policnik system, as a complex set of mutually interrelated Dinaric karst catchments and sub-catchments, is a highly vulnerable and limited groundwater source for the wider Zadar area in northern Dalmatia, Croatia. Based on hydrogeological, hydrochemical, and hydrological research, including the prediction of groundwater discharge by the end of the twenty-first century, a complex study was performed with the following main aims: (1) groundwater protection in the present state, (2) assessment of future groundwater protection, and (3) prediction of drinking water availability and quality under the predicted climate change conditions. Long-term prediction of changes in groundwater quantity, as well as investigations of trends in groundwater quality, will allow us to protect this essential natural resource with respect to possible negative trends. The results showed that a significant decrease in the quantity of available groundwater is possible and that extraction will have to be well planned because any decrease in the groundwater pressure in this area will cause a further decrease in quality, especially regarding the possibility of seawater intrusions into the aquifer. The results of this study were incorporated in sanitary protection zones.

Assessing seasonal and long-term changes in groundwater quality due to over-abstraction using geostatistical techniques

Future climate change and the temporal variability of water availability may cause the deterioration of groundwater quality and increase depths to water tables. In this study, groundwater quality data of 347 monitoring sites from 2003 to 2016 from a region in Pakistan were used to analyze the spatiotemporal variability in different water quality parameters using the Mann–Kendall and Sen’s slope estimator tests. The results indicated a significant increasing trend (SIT) at 23% sites in pre-SAR (sodium adsorption ratio during the pre-monsoon season) and at 22% sites in pre-EC (electrical conductivity during the pre-monsoon season) over the entire study period. The spatial distribution modeling of groundwater quality trends indicated that a significant increasing trend was observed in EC at most of the monitoring sites during the pre-monsoon season (α = 0.05). The area with significant increasing trend of groundwater EC and SAR values increased during the pre-monsoon season and decreased during the post-monsoon season. A continuous significant increasing trend in EC and SAR was observed in the northern part of the study area during the period 2003–2016. This trend indicates that excessive groundwater abstraction in the area is causing adverse impacts on groundwater quality, and that management measures need to be urgently implemented to limit further degradation of groundwater quality.

Temperature-associated changes in groundwater quality

Climate change and urbanization are currently leading to a warming of the subsurface worldwide with yet unforeseen consequences for groundwater quality. The temperature-sensitivity of chemical and biological processes suggests that small temperature changes driven by current warming should have a detectable effect on the ecology of aquifers and the composition of groundwater itself, but field observations covering temperatures that are environmentally relevant are sparse. The analysis of a large data set provides field-scale evidence that, within the naturally occurring temperature range between 5 and 20 °C, temperature affects the quality of groundwater. A difference in temperature of +1 K is linked to a 4% decline in oxygen saturation and a pH drop of 0.02 due to the accumulation of carbon dioxide. Further, warmer groundwater shows signs of enhanced mineral weathering and higher concentrations of drinking water-relevant elements such as manganese. The observed trends in groundwater quality are consistent with a temperature-associated intensification of microbial metabolic rates and enhanced organic matter mineralization at warmer temperatures either within the aquifers or in the overlying soils. A times series analysis reveals that soil and groundwater temperatures in the studied area have been increasing at a rate of 0.1–0.4 K per decade -comparable to recent global warming- driving subtle, but distinct changes in groundwater pH and oxygen concentrations. The results confirm, that certain but central aspects of groundwater quality (pH, O2, pCO2, Mn, DOC) change due to warming, which may increase the costs for purification when drinking water is produced from groundwater resources and may turn some aquifers uninhabitable for groundwater biota.

Land use change and conversion effects on ground water quality trends: An integration of land change modeler in GIS and a new Ground Water Quality Index developed by fuzzy multi-criteria group decision-making models

This study aggregated Land Change Modeller (LCM) as a useful model in GIS with an extended Groundwater Quality Index (GWQI) developed by fuzzy Multi-Criteria Group Decision-Making models to investigate the effect of land use change and conversion on groundwater quality being supplied for drinking. The model's performance was examined through an applied study in Shiraz, Iran, in a five year period (2011 to 2015). Four land use maps including urban, industrial, garden, and bare were employed in LCM model and the impact of change in area and their conversion to each other on GWQI changes was analysed. The correlation analysis indicated that increase in the urban land use area and conversion of bare to the residential/industrial land uses, had a relation with water quality decrease. Integration of LCM and GWQI can accurately and logically provide a numerical analysis of the possible impact of land use change and conversion, as one of the influencing factors, on the groundwater quality. Hence, the methodology could be used in urban development planning and management in macro level.

Prediction of Groundwater Quality Trends Resulting from Anthropogenic Changes in Southeast Florida.

The effects of surface water flow system changes caused by constructing water-conservation areas and canals in southeast Florida on groundwater quality under the Atlantic Coastal Ridge was investigated with numerical modeling. Water quality data were used to delineate a zone of groundwater with low total dissolved solids (TDS) within the Biscayne aquifer under the ridge. The delineated zone has the following characteristics. Its location generally coincides with an area where the Biscayne aquifer has high transmissivities, corresponds to a high recharge area of the ridge, and underlies a part of the groundwater mound formed under the ridge prior to completion of the canals. This low TDS groundwater appears to be the result of pre-development conditions rather than seepage from the canals constructed after the 1950s. Numerical simulation results indicate that the time for low TDS groundwater under the ridge to reach equilibrium with high TDS surface water in the water-conservation areas and Everglades National Park are approximately 70 and 60 years, respectively. The high TDS groundwater would be restricted to the water-conservation areas and the park due to its slow eastward movement caused by small hydraulic gradients in Rocky Glades and its mixing with the low TDS groundwater under the high-recharge area of the ridge. The flow or physical boundary conditions such as high recharge rates or low hydraulic conductivity layers may affect how the spatial distribution of groundwater quality in an aquifer will change when a groundwater flow system reaches equilibrium with an associated surface water flow system.