Surface Water And Groundwater Research Articles

Groundwater–Surface Water Exchange and Spatial Distribution of Arsenic in Arid and Semi-Arid Regions: The Case of Aksu River in Xinjiang, Northwestern China

The Aksu River, a quintessential inland river, exhibits elevated arsenic (As) concentrations in certain sections of its natural waters. Further investigation is necessary to determine the role of surface water and groundwater (SW-GW) exchanges in contributing to these high As concentrations. Both surface water and groundwater constitute crucial components of the basin water cycle, and the interaction between the two has been a central focus in basin water cycle research. In this study, a total of 59 groundwater samples and 41 surface water samples were collected along the river’s course within the basin. Among the groundwater samples, 18.64% exceeded the permissible drinking limit for As concentrations (10 μg/L), while 39.02% of the surface water samples exceeded this threshold. The water bodies in the Aksu River Basin are mildly alkaline, with total dissolved solids (TDSs) in surface water significantly surpassing those in groundwater. The chemical compositions of surface water and groundwater are strikingly similar, with the predominant anions being chloride (Cl−) and sulfate (SO42−) and the principal cations being sodium (Na+). The dissolution of silicate and carbonate minerals primarily influences the water chemistry characteristics of surface water and groundwater in the Aksu River Basin, followed by the dissolution of salt rocks. Human activities also play a major role in affecting the river’s water quality. The distribution of groundwater with elevated As content is entirely encompassed within the spatial distribution of surface water. Groundwater–surface water exchange plays a vital role in As enrichment in surface water.

Enhanced Hydrological Simulations in Paddy-Dominated Watersheds Using the Hourly SWAT-MODFLOW-PADDY Modeling Approach

Accurate hydrological simulations are crucial for managing water resources and promoting sustainable agriculture in submerged paddy agricultural watersheds. The SWAT-MODFLOW, which couples the Soil and Water Assessment Tool (SWAT) and the Modular Groundwater Flow (MODFLOW) model, is a widely used tool for hydrologic simulations that consider surface water and groundwater (SW-GW) interactions. However, it falls short of effectively simulating the hydrological processes of submerged rice paddy field areas. To address this, we developed the hourly SWAT-MODFLOW-PADDY model, which enables integrated surface and groundwater simulations and effectively represents the hydrological responses of submerged paddy fields to high-resolution rainfall data. Our findings demonstrated that the hourly SWAT-MODFLOW-PADDY model could dynamically simulate soil moisture and runoff patterns in submerged paddy fields. Notably, the developed model showed enhanced performance throughout the entire period for hourly flow in the watershed, with an average coefficient of determination (R2) of 0.75, Nash and Sutcliffe efficiency (NSE) of 0.76, and percent bias (PBIAS) of 13.22 compared to the original model (R2 = 0.62, NSE = 0.70, PBIAS = 48.21). The model’s performance in predicting water quality was improved, and it highlighted the significant impact of complex hydrological mechanisms within submerged paddy fields on the spatial distribution of groundwater recharge and stream water volumes exchanged through SW-GW interactions. Given these promising results, the SWAT-MODFLOW-PADDY model could be a valuable resource for managing submerged paddy-dominated agricultural watersheds across various climates and regions.

Study on Interaction between Surface Water and Groundwater in Typical Reach of Xiaoqing River Based on WEP-L Model

Surface water and groundwater (SW-GW) are an inseparable whole, having a tightly coupled hydraulic relationship and frequent inter-transformation. As such, the quantitative calculation of water exchange between SW-GW is a difficult challenge. To address this issue, we propose the use of a physically based and distributed hydrological model, called WEP-L, in order to analyze the effects of the SW-GW interaction and its spatiotemporal variation characteristics in the Xiaoqing River basin. We demonstrate that the SW-GW interaction is significantly affected by season. The simulated annual average exchange volume of SW-GW above the control section of Huangtaiqiao Station from 1980 to 2020 is found to be 54.79 m3/s. The exchange volumes of SW-GW in the wet and dry season are 28.69 m3/s and 13.46 m3/s, respectively, accounting for 48.75% and 22.87% of the whole year. In addition, considering two types of climate change scenarios, the exchange capacity of SW-GW increases by 0.42m3/s when the rainfall increases by 5%, while the exchange capacity decreases by only 0.2 m3/s when the temperature increases by 0.2 °C. This study provides insights for the quantification of the SW-GW interaction at the regional scale, which will benefit our understanding of the water cycle and evolution of water resources in Xiaoqing River basin.

Protection of peri-urban groundwater catchments: a multi-tracer approach for the identification of urban pollution sources

Abstract. Groundwater catchment located in peri-urban areas may be impacted by many pollutants coming from different types of point or diffuse sources such as accidental spills, continuous hidden leaks in drainage networks, old landfills, treated/untreated wastewater and watercourses. In the scope of the CASPER project, a new methodological approach has been developed based on field survey and interpretation of the collected data in order to distinguish between the different sources of contamination and mixtures of pollutants. First, the groundwater catchment area corresponding to the land surface perimeter in which abstracted groundwater is recharged is determined and characterised in hydrogeological terms. The possible sources of pollution are identified. In a second step, a groundwater and surface water monitoring survey is established, and water samples are collected focusing on a combination of physicochemical parameters and set of various hydrochemical indicators. In particular, different stable isotopes are considered. The NO3- and Boron stable isotopes are used to distinguish between inputs linked to urban effluents, agricultural fertilisers and manure. Stable isotopes of SO42- are used to distinguish between sulphide minerals oxidation, sulphur-carbon compounds mineralisation, lixiviation and human pollution. Moreover, the occurrence of specific molecules like pharmaceutical and lifestyle products (carbamazepine, caffeine, etc.) are used as effective tracers of anthropogenic contamination. Microbiological analyses are also undertaken to identify microbial populations associated with specific sources of pollution or specific biochemical reactions occurring in soil and groundwater. The resulting hydrochemical dataset is then processed using multivariate and clustering analyses. In this context, the objective here is to describe the rigorous methodological approach to assess pollution sources and to illustrate the first steps of this process using a case study corresponding to a groundwater catchment is a chalk aquifer in Western Belgium.

Small-scale topography explains patterns and dynamics of dissolved organic carbon exports from the riparian zone of a temperate, forested catchment

Abstract. Export of dissolved organic carbon (DOC) from riparian zones (RZs) is an important component of temperate catchment carbon budgets, but export mechanisms are still poorly understood. Here we show that DOC export is predominantly controlled by the microtopography of the RZ (lateral variability) and by riparian groundwater level dynamics (temporal variability). From February 2017 until July 2019 we studied topography, DOC quality and water fluxes and pathways in the RZ of a small forested catchment and the receiving stream in central Germany. The chemical classification of the riparian groundwater and surface water samples (n=66) by Fourier transform ion cyclotron resonance mass spectrometry revealed a cluster of plant-derived, aromatic and oxygen-rich DOC with high concentrations (DOCI) and a cluster of microbially processed, saturated and heteroatom-enriched DOC with lower concentrations (DOCII). The two DOC clusters were connected to locations with distinctly different values of the high-resolution topographic wetness index (TWIHR; at 1 m resolution) within the study area. Numerical water flow modeling using the integrated surface–subsurface model HydroGeoSphere revealed that surface runoff from high-TWIHR zones associated with the DOCI cluster (DOCI source zones) dominated overall discharge generation and therefore DOC export. Although corresponding to only 15 % of the area in the studied RZ, the DOCI source zones contributed 1.5 times the DOC export of the remaining 85 % of the area associated with DOCII source zones. Accordingly, DOC quality in stream water sampled under five event flow conditions (n=73) was closely reflecting the DOCI quality. Our results suggest that DOC export by surface runoff along dynamically evolving surface flow networks can play a dominant role for DOC exports from RZs with overall low topographic relief and should consequently be considered in catchment-scale DOC export models. We propose that proxies of spatial heterogeneity such as the TWIHR can help to delineate the most active source zones and provide a mechanistic basis for improved model conceptualization of DOC exports.

Characteristics and Significance of Environmental Isotopes and Hydrochemistry in Surface Water and Groundwater in Jixi Wetland, East China

The interaction between surface water and ground water (SW-GW) is an important mechanism affecting wetland hydrological process and its ecological environment. Jixi Wetland, located in the western part of Jinan City, East China, was selected as the study area. The surface water bodies include Yuqinghu Reservoir, Yellow River, Yufu River, Jiping Trunk Channel and Xiaoqing River. Groundwater includes shallow pore water and deep fracture karst water. To strengthen water management and protection and understand different water exchange in the Jixi Wetland, ion composition, stable isotopes (δ18O and δ2H) and deuterium excess were studied. The result shows that the characteristic cation is Ca2+, and the characteristic anion is HCO3 −. The main hydrochemical types of wetland water, Sedimentation Basin water and groundwater are HCO3⋅Cl - Ca⋅Mg water, the water of Jiping Trunk Channel is HCO3⋅Cl - Na⋅Mg type, the water of Yufu River is HCO3⋅Cl - Ca⋅Na type, and the water of Yellow River is HCO3⋅Cl - Na⋅Ca type. There is a hydraulic connection between SW-GW. The evaporation is strong in the surface water, while it plays a weak role in the groundwater. The dominant hydrogeochemical processes in the study area are lixiviation and cation alternating adsorption.

Variation of lake-river-aquifer interactions induced by human activity and climatic condition in Poyang Lake Basin, China

In low-lying fluvial-lacustrine plain, anthropogenic activities and climatic variation could have a comprehensive influence on the interactions between surface water and groundwater (SW-GW) involving lake-river-aquifer. Quantification of the changes in SW-GW interaction in spatial and temporal scale causing by the two driving sources could help to the understanding of the regional water cycle mechanism and the adjustment of the decision making. However, it is usually difficult to distinguish the impact of anthropogenic activities from the climatic variation on a regional scale. Here, by using a regional three-dimensional groundwater numerical model with long term monitoring of the hydrological dynamic in Poyang Lake Basin (PLB), China, we found that groundwater storage variation in the bank storage districts can be used as an indicator to quantify each source and sink in the process of SW-GW interactions. And surface water infiltration plays a more dominant role in constructing bank storage which is meant to preserve groundwater storage. Our research in PLB demonstrates that the hydrological change caused by the operation of the Three Gorges Dam (TGD) since 2003 is mainly responsible for the autumn drought in PLB. The surface water recession due to the impoundment in TGD from September to October has an impact about 7 times stronger than the rainfall reduction. Moreover, the groundwater storage deficit caused by the insufficient recharge from the surface water infiltration would maintain the whole year, unlike the surface water system which would easily recover at the end of the year. The results demonstrate the chain interactions among lake-river-aquifer. Failing to distinguish the magnitude of each influence factor may lead to underestimating the impact on the whole water system. The results also highlight the function and the vulnerability of the groundwater system which might be vital to the riparian and estuarine-wetland ecosystem.

A review of conjunctive GW-SW management by simulation–optimization tools

Abstract The conjunctive use of groundwater and surface water (GW-SW) resources has grown worldwide. Optimal conjunctive water use can be planned by coupling hydrologic models for the simulation of water systems with optimization techniques for improving management strategies. The coupling of simulation and optimization methods constitutes an effective approach to determine sustainable management strategies for the conjunctive use of these water resources; yet, there are challenges that must be addressed. This paper reviews (1) hydrologic models applied for the simulation of GW-SW interaction in the water resources systems, (2) conventional optimization methods, and (3) published works on optimized conjunctive GW-SW use by coupling simulation and optimization methods. This paper evaluates the pros and cons of GW-SW simulation tools and their applications, thus providing criteria for selecting simulation–optimization methods for GW-SW management. In addition, an assessment of GW-SW simulation–optimization tools applied in various studies over the world creates valuable knowledge for selecting suitable simulation–optimization tools in similar case studies for sustainable water resource management under multiple scenarios.

Solute exchanges between multi-depth groundwater and surface water of climatically vulnerable Gangetic delta front aquifers of Sundarbans

The coastal aquifers of Sundarbans, an UNESCO world biodiversity heritage site, are highly vulnerable due to changing climatic conditions, intensification and increasing frequency of extreme climate events and uncontrolled abstraction of groundwater. The exchange of solutes between hydraulically connective shallow and deep aquifers, the seawater intrusion and the role of growing population are poorly understood in the Sundarbans. This study aims to address the solute exchange (Cl−, Sr2+, and salinity) process between surface water and groundwater (SW-GW) at local to regional scale under variable hydraulic head conditions, where annual rainfall is declining and population density is increasing [population 573 (1991) to 819 (2011)/Km2]. Electrical resistivity tomography (ERT) in combination with salinity and δ18O data was used to address the exchange of solutes between SW-GW in a hydraulic continuation. The results revealed that regionally, the Cl− concentration of Sundarbans shows an increasing trend (average 329–351 mg/L) with declining groundwater levels (⁓3 m). Local, depth-dependent study depicting there is a predominant exchange of Sr2+ between shallow depth [D1: 14–25 and D2: 30–50 m below ground level (m bgl)] with seawater (Sr2+: 30–85 μM), which is possibly absent at greater depths (D3:115 and D4: 333 m bgl). The recorded Sr2+ content ranged from 25 to 102 and 16 to 78 μM for shallow depth D1 and D2, respectively, whereas, the Sr2+ concentrations ranged from 1.4 to 6.8 and 1.2 to 5.7 μM for D3 and D4, respectively. The ERT data showed progressively increasing resistivity with increasing depth, similar to high salinity and enriched δ18O at shallow depths and depleted δ18O with low salinity at higher depth reflects the continuous distribution of solutes, which is possibly a result of local downward migration of contaminated shallow brackish water within this physically disconnected zone. The lateral and vertical transportation of solutes in variable hydraulic head conditions would be a measure of drinking water threat in present-day and in imminent future for millions of inhabitants near the coastal area.

Surface Water and Groundwater Interactions in Wetlands

Wetland ecosystems are critical habitats for various types of wild lives and are important components of global ecosystem. However, with climate change and human activities, wetlands are facing with degradation. Surface water and groundwater (SW-GW) interactions play an essential role in matter and energy cycling in wetlands, and therefore affect the evolution and health of wetlands. But the role of groundwater in wetland ecosystems has been neglected or simplified. In this paper, we reviewed how surface water interacts with groundwater, and made a systematic summarization of the role of SW-GW interactions (such as maintaining water balance and biological diversity and removing pollution) in wetland ecological functions. We also reviewed the methods to investigate, simulate and quantify SW-GW interactions and related reactions. Finally, we illustrated how climate change and human activities affect SW-GW interactions and therefore affect wetland functions. We highlight the importance of groundwater in wetlands and the urgency to intensify the research in integrated multidisciplinary monitoring and simulation methods, dominant variables and thresholds and integrated water resources management of SW-GW interactions, and further aim to stimulate better protection and restoration of wetlands all over the world.

Factors influencing surface water and groundwater interaction in alluvial fan

Abstract In this study, the surface water balance method was used to calculate the interaction between surface water and groundwater (SGW) in the Taoer River alluvial fan in Jilin Province, China, from 1956 to 2014. The automatic linear model was used to determine the key and non-key influencing factors, and correlation analysis was performed to evaluate their relationship with one another. River runoff and groundwater level were the key factors affecting the SGW interaction, and sand–gravel exposure in the fan was more conducive to SGW interaction. There was a positive correlation between runoff and SGW interaction, and the relationship between the groundwater and surface water levels was correlated and affected by groundwater exploitation and groundwater runoff. Groundwater exploitation and evaporation and precipitation indirectly influenced the SGW interaction by affecting the groundwater level and river runoff key factors, respectively, and were considered non-key factors.

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Abstract. Increased anthropogenic inputs of nitrogen (N) to the biosphere during the last few decades have resulted in increased groundwater and surface water concentrations of N (primarily as nitrate), posing a global problem. Although measures have been implemented to reduce N inputs, they have not always led to decreasing riverine nitrate concentrations and loads. This limited response to the measures can either be caused by the accumulation of organic N in the soils (biogeochemical legacy) – or by long travel times (TTs) of inorganic N to the streams (hydrological legacy). Here, we compare atmospheric and agricultural N inputs with long-term observations (1970–2016) of riverine nitrate concentrations and loads in a central German mesoscale catchment with three nested subcatchments of increasing agricultural land use. Based on a data-driven approach, we assess jointly the N budget and the effective TTs of N through the soil and groundwater compartments. In combination with long-term trajectories of the C–Q relationships, we evaluate the potential for and the characteristics of an N legacy. We show that in the 40-year-long observation period, the catchment (270 km2) with 60 % agricultural area received an N input of 53 437 t, while it exported 6592 t, indicating an overall retention of 88 %. Removal of N by denitrification could not sufficiently explain this imbalance. Log-normal travel time distributions (TTDs) that link the N input history to the riverine export differed seasonally, with modes spanning 7–22 years and the mean TTs being systematically shorter during the high-flow season as compared to low-flow conditions. Systematic shifts in the C–Q relationships were noticed over time that could be attributed to strong changes in N inputs resulting from agricultural intensification before 1989, the break-down of East German agriculture after 1989 and the seasonal differences in TTs. A chemostatic export regime of nitrate was only found after several years of stabilized N inputs. The changes in C–Q relationships suggest a dominance of the hydrological N legacy over the biogeochemical N fixation in the soils, as we expected to observe a stronger and even increasing dampening of the riverine N concentrations after sustained high N inputs. Our analyses reveal an imbalance between N input and output, long time-lags and a lack of significant denitrification in the catchment. All these suggest that catchment management needs to address both a longer-term reduction of N inputs and shorter-term mitigation of today's high N loads. The latter may be covered by interventions triggering denitrification, such as hedgerows around agricultural fields, riparian buffers zones or constructed wetlands. Further joint analyses of N budgets and TTs covering a higher variety of catchments will provide a deeper insight into N trajectories and their controlling parameters.

Regularity and a statistical model of surface water and groundwater interaction in the Taoer River alluvial fan, China

Abstract The study of surface water and groundwater (SGW) interaction can be used to improve water resource management. Herein, annual and monthly interactions in the Taoer River alluvial fan were calculated for the 1956–2014 period using the surface water balance method and the groundwater balance method, and a statistical model of interaction was obtained. The SGW interaction is shown in terms of the recharge of groundwater by surface water. From 1956 to 2014, the amount of SGW interaction in the study area varied greatly, averaging 27,848.4 × 104m3 annually. SGW interaction decreased gradually from the 1950s to the 1980s, and increased gradually from the 1980s to the present. During an individual year, SGW interaction increases gradually from January to July, peaking in July, and decreases gradually from August to December. An annual and a monthly multivariate regression statistical model were established. R2 was 0.697 for the annual model and 0.405 for the monthly model; the annual interaction model is more reliable. The model can be used to predict future trends in SGW interaction, which could be of great significance to the management of groundwater resources in the study area.

Grey water footprint reduction in irrigated crop production: effect of nitrogen application rate, nitrogen form, tillage practice and irrigation strategy

Abstract. Grey water footprint (WF) reduction is essential given the increasing water pollution associated with food production and the limited assimilation capacity of fresh water. Fertilizer application can contribute significantly to the grey WF as a result of nutrient leaching to groundwater and runoff to streams. The objective of this study is to explore the effect of the nitrogen application rate (from 25 to 300 kg N ha−1), nitrogen form (inorganic N or manure N), tillage practice (conventional or no-tillage) and irrigation strategy (full or deficit irrigation) on the nitrogen load to groundwater and surface water, crop yield and the N-related grey water footprint of crop production by a systematic model-based assessment. As a case study, we consider irrigated maize grown in Spain on loam soil in a semi-arid environment, whereby we simulate the 20-year period 1993–2012. The water and nitrogen balances of the soil and plant growth at the field scale were simulated with the Agricultural Policy Environmental eXtender (APEX) model. As a reference management package, we assume the use of inorganic N (nitrate), conventional tillage and full irrigation. For this reference, the grey WF at a usual N application rate of 300 kg N ha−1 (with crop yield of 11.1 t ha−1) is 1100 m3 t−1, which can be reduced by 91 % towards 95 m3 t−1 when the N application rate is reduced to 50 kg N ha−1 (with a yield of 3.7 t ha−1). The grey WF can be further reduced to 75 m3 t−1 by shifting the management package to manure N and deficit irrigation (with crop yield of 3.5 t ha−1). Although water pollution can thus be reduced dramatically, this comes together with a great yield reduction, and a much lower water productivity (larger green plus blue WF) as well. The overall (green, blue and grey) WF per tonne is found to be minimal at an N application rate of 150 kg N ha−1, with manure, no-tillage and deficit irrigation (with crop yield of 9.3 t ha−1). The paper shows that there is a trade-off between grey WF and crop yield, as well as a trade-off between reducing water pollution (grey WF) and water consumption (green and blue WF). Applying manure instead of inorganic N and deficit instead of full irrigation are measures that reduce both water pollution and water consumption with a 16 % loss in yield.

Potential for Small Unmanned Aircraft Systems Applications for Identifying Groundwater‐Surface Water Exchange in a Meandering River Reach

AbstractThe exchange of groundwater and surface water (GW‐SW), including dissolved constituents and energy, represents a critical yet challenging characterization problem for hydrogeologists and stream ecologists. Here we describe the use of a suite of high spatial resolution remote sensing techniques, collected using a small unmanned aircraft system (sUAS), to provide novel and complementary data to analyze GW‐SW exchange. sUAS provided centimeter‐scale resolution topography and water surface elevations, which are often drivers of exchange along the river corridor. Additionally, sUAS‐based vegetation imagery, vegetation‐top elevation, and normalized difference vegetation index mapping indicated GW‐SW exchange patterns that are difficult to characterize from the land surface and may not be resolved from coarser satellite‐based imagery. We combined these data with estimates of sediment hydraulic conductivity to provide a direct estimate of GW “shortcutting” through meander necks, which was corroborated by temperature data at the riverbed interface.

Optical sensing using fiber bragg gratings: fundamentals and applications

In this article, Fiber Bragg Grating (FBG) technology used to implement fiber sensors is explained and some applications in temperature and strain measurements are presented. In the first section, the fundamentals and operation principles of FBGs are shown as well as optical fiber sensing interrogators. The second part of the article presents applications of temperature measurements in power transmission lines, shrinkage measurements in concrete structures, and spatiotemporal measurement variations in variations of temperature between groundwater and surface water (GW-SW).

PROMINE

The condition of water, soil and rock in Bangka Belitung University can be one of reference forconservation area and future development. Field observation known that the research location isgrouped into formation of sedimentary is Tanjung Genting Formation. Average pH of water 5,3; TDS41.1 mg/l; TSS 11,1 mg/l and Al content 0,18 mg/l; Fe 0.32 mg/l; Cu 0.14 mg/l taken from groundwaterand surface water samples. Rock samples of static test results obtained that the rocks are acidic butinto the category is uncertain. However, from the paste pH it was found that the pH of rocks is 5,39and this shows that the rocks are not potentially acidic.

Identifying the regional-scale groundwater-surface water interaction on the Sanjiang Plain, Northeast China.

Assessment on the interaction between groundwater and surface water (GW-SW) can generate information that is critical to regional water resource management, especially for regions that are highly dependent on groundwater resources for irrigation. This study investigated such interaction on China's Sanjiang Plain (10.9 × 10(4) km(2)) and produced results to assist sustainable regional water management for intensive agricultural activities. Methods of hierarchical cluster analysis (HCA), principal component analysis (PCA), and statistical analysis were used in this study. One hundred two water samplings (60 from shallow groundwater, 7 from deep groundwater, and 35 from surface water) were collected and grouped into three clusters and seven sub-clusters during the analyses. The PCA analysis identified four principal components of the interaction, which explained 85.9% variance of total database, attributed to the dissolution and evolution of gypsum, feldspar, and other natural minerals in the region that was affected by anthropic and geological (sedimentary rock mineral) activities. The analyses showed that surface water in the upper region of the Sanjiang Plain gained water from local shallow groundwater, indicating that the surface water in the upper region was relatively more resilient to withdrawal for usage, whereas in the middle region, there was only a weak interaction between shallow groundwater and surface water. In the lower region of the Sanjiang Plain, surface water lost water to shallow groundwater, indicating that the groundwater was vulnerable to pollution by pesticides and fertilizers from terrestrial sources.

Assessment of ground and surface water quality along the river Varuna, Varanasi, India.

Multivariate statistical techniques were employed for monitoring of ground-surface water interactions in rivers. The river Varuna is situated in the Indo-Gangetic plain and is a small tributary of river Ganga. The study area was monitored at seven sampling sites for 3 years (2010-12), and eight physio-chemical parameters were taken into account for this study. The data obtained were analysed by multivariate statistical techniques so as to reveal the underlying implicit information regarding proposed interactions for the relevant area. The principal component analysis (PCA) and cluster analysis (CA), and the results of correlations were also studied for all parameters monitored at every site. Methods used in this study are essentially multivariate statistical in nature and facilitate the interpretation of data so as to extract meaningful information from the datasets. The PCA technique was able to compress the data from eight to three parameters and captured about 78.5% of the total variance by performing varimax rotation over the principal components. The varifactors, as yielded from PCA, were treated by CA which grouped them convincingly into three groups having similar characteristics and source of contamination. Moreover, the loading of variables on significant PCs showed correlations between various ground water and surface water (GW-SW) parameters. The correlation coefficients calculated for various physiochemical parameters for ground and surface water established the correlations between them. Thus, this study presents the utility of multivariate statistical techniques for evaluation of the proposed interactions and effective future monitoring of potential sites.

Interactions Between Surface Water and Groundwater: Key Processes in Ecological Restoration of Degraded Coastal Wetlands Caused by Reclamation

Interactions between surface water and groundwater (SW-GW), composed of complex hydrological networks, maintain a dynamic balance between water regimes and salinity in coastal wetlands. Impacted by reclamation activity, however, changes in water regimes and salinity have resulted in wetland degradation. To mitigate such reclamation impacts on coastal wetlands, it is vital to understand the role of SW-GW interactions involved in maintaining the integrity of coastal wetlands. The objectives of this review were to: (i) outlining SW-GW interactions; (ii) addressing ecological responses to changes in water regimes and salinity; and (iii) exploring modeling techniques used to ascertain interactions between groundwater and coastal wetlands. Key findings are as follows: SW-GW interactions control water regimes and salinity while maintaining the integrity of coastal wetlands; the combined effects of water and salinity have an impact on ecological processes and patterns disturbed by hydrological pulses; and the distribution of physically-based models is an approach that can provide a profound means by which to understand the vital role in maintaining hydrological connectivity. Further research is required to fully reveal SW-GW interactions in maintaining coastal wetlands integrity and the mitigating effects reclamation has on coastal wetlands.