Surface Groundwater Research Articles

Evaluating Spatiotemporal Variations of Groundwater–Surface Water Interaction Using an Integrated Hydrological Model in Huashan Basin, China

Quantifying the spatiotemporal variations of basin-scale surface water (SW)–groundwater (GW) interactions is vital for the conjunctive management of water resources in the basin. In this study, an integrated hydrological model (SWAT-MODFLOW) is used to simulate the SW–GW system in the Huashan Basin. The numerical model was calibrated and validated using the streamflow observations of the watershed outlet and the groundwater levels of the long-term monitoring wells from 2016 to 2020 in the study area. The model results show that the SWAT–MODFLOW can achieve a better fit for the streamflow discharge, compared with the results in the single SWAT model, with R2 (coefficient of correlation) and NSE (Nash-Sutcliffe efficiency coefficient) of 0.85 and 0.83, respectively. The water table fitting results indicate that R2 and RMSE can reach 0.95 and 0.88, respectively. The water budgets analysis demonstrates that the average rate (0.5281 m3/s) of GW abstraction to SW is larger than the rate (0.1289 m3/s) of SW recharge to GW. Moreover, the exchange rate of SW and GW gradually reaches a peak value from June to August, and the lowest value is shown in April, for each hydrological year. Based on the IPPC6 CanESM5 dataset supplied by the Canadian Climate Centre, the regional precipitation scenario subject to climate change was predicted by the ASD (Auto Statistical Downscaling Model) a statistical downscaling method, under the climate scenarios of SSP2_4.5 and SSP5_8.5. The SW–GW interaction pattern was modeled under the future scenarios in the study area. The current (2016–2020) average annual rate of the SW–GW interaction is considered as the base value. Subject to the SSP2_4.5 scenario, the average exchange rate of the SW recharge to GW is 0.1583 m3/s, which is an increase of 22.8%. The average exchange rate of the GW discharge to SW is 0.5189 m3/s which is a reduction of 0.017%. Subject to the SSP5_8.5 scenario, the average exchange rate of SW recharge to GW is 0.1469 m3/s, which is an increase of 14.7%. The average exchange rate of the GW discharge to SW is 0.5953 m3/s, which is an increases of 12.7%. The results can assist in water resource management in the basin, by identifying potential locations of nutrient transport from the aquifer to the river, as well as changes in spatial variability under future climatic conditions.

Triethanolamine-modulated interfacial polymerization toward microcrumpled nanofiltration membranes: Performances and mechanisms

Highly permeable thin-film composite (TFC) nanofiltration (NF) membranes featuring high separation efficiencies are of great importance for purifying surface water and ground water. Increasing the filtration area of NF membranes via accurate control of the interfacial polymerization (IP) is proposed to be an efficient way to achieve this goal. In this work, a triethanolamine (TEOA)-modulated IP was utilized to tailor the IP reaction rate and thus regulate the separation performance of NF membranes. The resultant NF membranes were characterized in terms of chemical structures, morphologies, and separation behaviors in detail. The reaction dynamic of the TEOA-doped IP was evaluated by stopped-flow spectroscopy and molecular dynamics. The results showed that the incorporation of TEOA could efficiently regulate the IP reaction rate through hydrogen bonds, increased viscosity, and acid-neutralization effects. As result, a high-performance NF membrane possessing a microcrumpled structure and excellent separation efficiency for ground water was achieved. Hence, the TEOA-modulated IP method is expected to be a maneuverable approach for tailoring excellent NF membranes for ground water treatments.

PARAMETRIC MODELLING OF THE GEOLOGICAL CROSS SECTION FOR SHIELD TUNNEL DESIGN AND CONSTRUCTION

Abstract. Geological information is indispensable for the design and construction of underground structures, especially for large-diameter shield tunnels. The geological cross-section is expected to be accurately and efficiently modelled to provide sufficient geological information for decision-making. However, the existing methods are usually time-consuming, and the calculation results cannot be intuitively understood by engineers. To meet this demand, this study attempts to develop a parametric modelling approach for the geological cross-section of tunnelling construction. The proposed approach consisted of four steps. In the first step, the borehole records from the geological investigation are converted into the DataFrame format. Then, each point is assigned a soil type label and soil property parameter to form a data framework. In the third step, the cross-section is generated in mesh type and divided into two parts. Finally, the mesh models are rendered to visualize the stratum sequence and soil property distribution. The proposed approach is applied to Lianghu tunnelling construction in Wuhan, China, for verification. The results show that the 11 geological cross-sections with ground water surfaces can be automatically modelled within 25 seconds, including stratum sequence identification and ground pressure calculation. The calculation results could be successively used in the tunnel structural analysis. Therefore, the proposed approach potentially promotes a data-driven technology for underground engineering construction.

Hydrological environment affects the nutrient retention and runoff function of naturally re-wetted agricultural peatland in lowland river floodplain

Re-wetting of agricultural areas reclaimed by draining peatlands reportedly entails risks of nutrient loads downstream because of leaching of dissolved nutrients from pools in the soil. On floodplain fens, nutrient retention and runoff function have been recognized as dependent upon the hydrological environments of re-wetted agricultural peatland (RAP). Although many studies have been conducted for artificially re-wetted agricultural peatlands (artificial RAPs), knowledge on naturally re-wetted agricultural peatlands (natural RAPs) has been lacking. This study assessed the natural re-wetting of agricultural areas in floodplain fens in terms of risks of nutrient loading in the basin of Kushiro Mire, northern Japan. Flooding of the adjacent river caused by heavy rainfall remarkably increased the water flow, and the inflow and outflow fluxes of nitrogen (N) and phosphorus (P) of a test plot in the natural RAP. Flood waters supplied mainly inorganic nutrients to the test plot, including NO3-N and PO4-P. Larger amounts of dissolved organic N and P, NH4-N, and PO4-P that had accumulated in surface water and surface groundwater in the plot flowed out. Consequently, the test plot represented net runoff of 3 and 0.4 mg m−2 day−1 as total N and total P, respectively, for the average of the whole observation period. The test plot was a source of N loading downstream, which was contrary to results obtained for artificial RAPs in many studies. However, the test plot showed a smaller amount of net phosphorus runoff. Our findings suggest that water level fluctuation and river flood water inflow affect the nutrient retention and runoff functions of RAPs. Repeated inundated and dried conditions, with no continuous inflow of river water, explain the nutrient runoff in the test plot.

Cooperation under conflict: participatory hydrological modeling for science policy dialogues for the Aculeo Lake

Abstract. Hydrological modeling tools can support collaborative decision processes by visually displaying hydrological systems connections, uncertainties, as well as conflicting preferences over water management strategies. Nevertheless, many challenges remain in the real application of these technical tools to successfully implement, capture, and communicate with non-experts the complexities of coupled human hydrological systems. A 5-step process shows how a WEAP-based hydrological study aiming to explore the disappearance of a 12 km2 lake in the Aculeo basin in Chile was transformed into a multiple question-driven sociohydrological modeling process to help answer the diversity of questions instigating conflict. Collaboration allowed construction of a surface–groundwater hydrological model that responded to local stakeholders' uncertainties. While testing a subset of socially accepted management strategies under two climate change scenarios, combining the strategies allows recovering up to half the lake water volume. However, the 5-step participatory modeling process also shows how the increasing social–environmental conflicts over the causes and effects of the water scarcity are challenging barriers to overcome with modeling tools. As presented in this article, although flexible approaches and research agendas could better support the exploration of synergies towards collaboration and production of useful and socially acceptable hydrological models, there are still value-driven aspects of water management that need to be explored to better support science policy dialogues.

Remote monitoring of minewater rebound and environmental risk using satellite radar interferometry

The cessation of dewatering following coalfield abandonment results in the rise of minewater, which can create significant changes in the local and regional hydrogeological regime. Monitoring such change is challenging but essential to avoiding detrimental consequences such as groundwater contamination and surface flooding. Inverse modelling methods using satellite radar interferometry (InSAR) have proven capable for retrospectively mapping minewater level changes, however, there is a need for the capability to remotely monitor changes as they occur. In this study, ground deformation measurements obtained from InSAR are used to develop a method to remotely monitor the spatio-temporal rise of minewater, which could be implemented in near real-time. The approach is demonstrated over the Horlivka mining agglomeration, Ukraine, where there is no other feasible approach possible due to a lack of safe ground access. The results were blindly validated against in-situ measurements before being used to forecast the time until minewater will reach the natural water table and Earth's surface. The findings reveal that, as a result of military conflict in Donbas, an environmental catastrophe could occur where potentially radioactive minewater is forecast to reach the natural water table between May and August of 2024.

Changing pattern of water supply system in Jaipur metropolitan (Rajasthan, India)

Jaipur is the capital and largest city of the Rajasthan state with a growing population of 4.008 million in 2021. Jaipur metropolitan is a fast-growing city that attracts the population to migrate from all over the state. Jaipur city is a well-known tourist center and the tourist footfall around the world is very high. The city is developing rapidly (in terms of industrial) and so the population is. This results in the lack of some of the basic necessities to cater to the demands of the population residing here. The major problem nowadays is water scarcity and the crisis that threatens drinking water sources. Due to scorching heat and semi-arid climatic conditions, the surface water sources of dams are drying up resulting in depleting water table. There is no perennial source of surface groundwater in the city. Initially, the Ramgarh dam was the source of drinking water for the city population. In the late 1980s/early 1990s, the major part of Ramgarh dam remained dried and till 2012 the river bed was completely dried. Jaipur city suffered in an acute situation in getting drinking water. Hence, a new source of water was investigated and constructed in 1990 i.e., Bisalpur dam located in Tonk district of Rajasthan over 120 km away from Jaipur, providing water to Tonk, Ajmer and Jaipur. The supply of water from Bisalpur Dam to Jaipur began in 2009. Due to the shortage of water supply from the Bisalpur dam, the government has planned and investigated a detailed feasibility report to link the Bisalpur dam to Chambal and Brahmini Rivers to make Bisalpur dam a sustainable water resource for utilizing excess water off the Brahmini River project. To combat such situation, it is very important for the government to find sustainable solutions. Besides this, public participation is also very significant to attain the solution.

Assessment of the slope influence on the pressure collecting drainage pipelines characteris-tics

A methodology for assessing the influence of the error value, which is included in the calculations of pressure drainage pipelines in the case of a groundwater surface slope, is proposed in the paper. It is based on the previously obtained solutions of the system of differential equations describing the liquid movement with variable flow rate in pressure drainage pipelines that operate at the horizontal level of the groundwater surface. The analysis is presented in dimensionless form. The influence of the groundwater level slope on the calculation results is estimated using the value of the relative flow variation in the end section of the collector and the generalized parameter of the collector drain A, which takes into account its design and filtration characteristics. The obtained calculation formulas are quite simple and easy to use. The proposed method allows to determine the limits within which simplified dependencies for the calculation of drainage pipelines can be used, which are recommended for use at the horizontal groundwater level on the land reclamation site. At the same time, the error introduced into the calculations as a result of the adopted simplification is immediately determined. Corresponding graphs are presented in the paper to illustrate the obtained dependencies.

Occurrences, transport drivers, and risk assessments of antibiotics in typical oasis surface and groundwater

Intensive use of antibiotics affects biogeochemical cycles and stimulates the evolution of antibiotic resistance, thus threatening global health and social development. The spatiotemporal distributions of antibiotics in single aqueous matrices have been widely documented; however, their occurrence in surface–groundwater systems has received less attention, especially in arid regions that usually have fragile ecosystems. Therefore, we investigated the occurrence of thirty-one antibiotics in the surface water and adjacent groundwater in the Xinjiang Uygur Autonomous Region, China. The results showed that the total concentrations of detected antibiotics varied from 17.37 to 84.09 ng L−1 and from 16.38 to 277.41 ng L−1 in surface and groundwater, respectively. The median concentration of antibiotics showed the pattern of norfloxacin (4.86 ng L−1) > ciprofloxacin (3.93 ng L−1) > pefloxacin (3.39 ng L−1) in surface water; whereas in groundwater, this was in the order of pefloxacin (6.30 ng L−1) > norfloxacin (4.33 ng L−1) > ciprofloxacin (2.68 ng L−1). Heatmap analysis indicated that vertical infiltration had limited effects on antibiotic exchange in surface–ground water systems because of the high potential evaporation and low water storage. Redundancy analysis suggested that the oxidation–reduction potential (p < 0.01) and dissolved oxygen (p < 0.05) jointly affected the distribution of antibiotics in surface water. Ecological risk assessment showed that antibiotics in 98.9% of surface water and 99.1% of groundwater did not pose significant risks to aquatic species. The findings of this study will help develop effective mitigation strategies for antibiotics in aquatic environments.

A comparative study of integral and coupled approaches for modeling hydraulic exchange processes across a rippled streambed

Although both are crucial parts of the hydrological cycle, groundwater and surface water had traditionally been addressed separately. In recent decades, considering them as a single hydrological continuum in light of their continuous interaction has become well established in the scientific community through the development of numerous measurement and experimental techniques. Nevertheless, numerical models, as necessary tools to study a wide range of scenarios and future event predictions, are still based on outdated concepts that consider groundwater and surface water separately. This study compares these “coupled models”, which result from the successive execution of a surface water model and a groundwater model, to a recently developed “integral model”. The integral model uses a single set of equations to model both groundwater and surface water simultaneously, and can account for the continuous interaction at their interface. For comparison, we investigated small-scale flow across a rippled porous streambed. Although we applied identical model domain details and flow conditions, which resulted in very similar water tables and pressure distributions, comparing the integral and coupled models yielded very dissimilar velocity values across the groundwater–surface water interface. These differences highlight the impact of continuous exchange across the interface in the integral model, which imitates such flow processes more realistically than the coupled model. A few decimeters away from the interface, modeled velocity fields are very similar. Since the integral model and the surface water component of the coupled model are both CFD-based (computational fluid dynamics), they require very similar computational resources, namely access to cluster computers. Unfortunately, replacing the surface water component of the coupled model with the widely used shallow water equations model, which indeed would reduce the computational resources required, produces inaccuracy.

An ensemble approach for predicting future groundwater levels in the Zagreb aquifer impacted by both local recharge and upstream river flow

This paper presents the first study assessing the climate change impact on groundwater levels of the Zagreb alluvial aquifer in Croatia by coupling climate projections under RCP8.5 for the period 2040–2070 with local scale groundwater flow modelling. As a novelty in groundwater modelling of climate change impacts, this study utilizes an ensemble of five climate models and two land surface models for providing projections of relevant boundary conditions to the groundwater model. The groundwater model is used for predicting climate driven changes in groundwater levels in the aquifer system influenced by both changes in local groundwater recharge and changes in river-flow. Both boundary conditions are obtained from the land surface models. In addition, the uncertainty contributions to groundwater levels from both climate models and land surface models were quantified using variance decomposition. The results revealed that the spatial pattern of changes in groundwater levels can be related to different processes influencing groundwater dynamics. In areas dominated by a strong groundwater-surface water interaction, close to the Sava river, the multi-model ensemble mean change in groundwater levels is negligible for low and average water levels. However, for high water levels, an increase was identified. In contrast, a decline in groundwater levels prevails in all areas where aquifer recharge is largely driven by rainfall infiltration. For the variance decomposition analysis, climate models were identified as the main source of uncertainty for groundwater levels. However, the uncertainty contribution of the choice of land surface model to the impact simulations was found to be more important in the area affected by a strong groundwater–surface water interaction and for periods of high groundwater levels. Also, specific local issues related to low and high groundwater levels that are associated with extreme hydrological regimes were found to exacerbate under climate projections.

Organic matter composition and inorganic nitrogen response to Hurricane Harvey’s negative storm surge in Corpus Christi Bay, Texas

Extreme weather events, such as tropical storms and hurricanes, are known to deliver large amounts of freshwater (surface runoff) and associated inorganic and organic nutrients to estuaries and the coastal ocean, affecting water quality and nutrient budgets. However, while Hurricane Harvey produced an unprecedented 1,000-year flood event in 2017 that inundated areas north of the landfall, like the Houston/Galveston region (Texas, United States), the impact on the Corpus Christi area, south of the landfall, was an intermittent negative surge (∼0.5 m below mean sea level (MSL)), caused by the southerly direction of winds and limited freshwater inflows. With the use of pre- and post-landfall surface-water, porewater, and groundwater nutrient measurements and dissolved organic matter (DOM) molecular characterization analyses, this study assessed the influence of negative storm surge on groundwater–surface water interactions and nutrient composition. Within 2 weeks following the first landfall, the forms and inputs of inorganic and organic nutrients fluctuated significantly nearshore Corpus Christi Bay. Sudden drops in sea level were correlated with pulses of NH4+ and disproportionately more dissolved organic carbon (DOC) than dissolved organic nitrogen (DON), likely from a carbon-rich groundwater or benthic source with slightly lower labile characteristics. Recovery to MSL drove higher proportions of nitrogenous DOM and lower dissolved inorganic nitrogen (DIN) inputs. An increased presence of sulfurized DOM derived from anaerobic microbial processing of organic matter mineralization in marine sediments post-landfall was facilitated by enhanced groundwater inputs and flushing of porewater due to considerable drops in sea level and steepening hydraulic gradients toward the coast. The induced pulses of higher groundwater advective fluxes are also hypothesized to have intermittently enhanced flushing of anoxic DIN and biodegraded DOM from porewater and groundwater and suggested that dynamic hurricane-induced negative surge events affect net nutrient budgets in estuarine and coastal seas.

Assessment of Cadmium and Copper Adsorption by Two Agricultural Soils from Romania and Tunisia: Risk of Water Resource Pollution

Using treated wastewater for irrigation is a good solution for conserving water, but it is also in part responsible for groundwater and water surface pollution by heavy metals, especially copper and cadmium. The soil can be a barrier to retaining these pollutants and protecting the water resource. This study presents an assessment of the adsorption of copper and cadmium by two agricultural soils from Tunisia and Romania to evaluate the risk of water pollution. At first, the two soils were characterized with a scanning electron microscope and different physico-chemical analyses. Before adsorption, the elemental analysis performed with an SEM showed a very low amount of cadmium and copper in both soils (0.01%). The Tunisian soil was considered clayey soil, and the Romanian soil was sandy clayey soil. All experimental kinetics and isotherms were well correlated (R2 &gt; 0.9) with the pseudo-first-order kinetic model and the modified and extended Redlich–Peterson binary adsorption model. For an initial concentration of both pollutants of 0.1 mmol·L−1, the amounts retained and the adsorption percentage of copper and cadmium by the two soils indicate that the Romanian soil (qCu = 0.87 μmol·g−1; % Cu = 98%; qCd = 0.88 μmol·L−1; % Cd = 99%) retained both pollutants better than the Tunisian soil (qCu = 0.65 μmol·g−1, %Cu = 83%; qCd = 0.73 μmol·g−1; %Cd = 93%). Copper presents the greatest risk of water resource pollution, especially in Tunisia. The SEM confirmed the soil adsorption of Cu and Cd and estimated that the retention mechanisms of these two heavy metals are mainly related to the amount of phosphorus, chloride, sulfur and carbon by complexation and precipitation reactions.

Groundwater input drives large variance in soil manganese concentration and reactivity in a forested headwater catchment

AbstractIn headwater catchments, surface groundwater discharge areas have unique soil biogeochemistry and can be hot spots for solute contribution to streams. Across the northeastern United States, headwater hillslopes with surface groundwater discharge were enriched in soil Mn, including Watershed 3 of Hubbard Brook Experimental Forest, New Hampshire. Soils of this site were investigated along a grid to determine extent of Mn‐rich zone(s) and relationships to explanatory variables using ordinary kriging. The O and B horizons were analyzed for total secondary Mn and Fe, Cr oxidation potential, total organic C, moisture content, wetness ratio, and pH. Two Mn hot spots were found: a poorly drained, flowing spring (Location A); and a moderately well‐drained swale (Location B). Both had ∼6,000–9,000 mg Mn kg–1 soil. However, Location A had high Cr oxidation potential (a measure of Mn reactivity), whereas Location B did not. Location C, a poorly drained seep with slow‐moving water, had lower Mn content and Cr oxidation potential. Manganese‐rich soil particles were analyzed using X‐ray absorption near‐edge structure and micro‐X‐ray diffraction; the dominant oxidation state was Mn(IV), and the dominant Mn oxide species was a layer‐type Mn oxide (L‐MnO2). We propose input of Mn(II) with groundwater, which is oxidized by soil microbes. Studies of catchment structure and response could benefit from identifying hot spots of trace metals, sourced mainly from parent material but which accumulate according to hydropedologic conditions. Small‐scale variation in Mn enrichment due to groundwater and microtopography appears to be more important than regional‐scale variation due to air pollution.

Joint operation of surface water and groundwater base on parallel-flower pollination algorithm

The joint operation of surface water and groundwater is an effective way to solve the shortage of water resources in arid areas of Northwest China, which is of great significance for efficient utilization of water resources. Taking the Heihe River Basin in Gansu Province as an example, this paper proposes two water supply mechanisms: groundwater based, surface water compensation and surface water based, and groundwater compensation. Taking the groundwater withdrawal and surface water reservoir level as optimization variables, a multi-objective model considering irrigation and ecology and considering hydropower generation is established, and Parallel Flower Pollination Algorithm (P-FPA) is introduced to solve the problem. The results show that the water supply mechanism based on groundwater and surface water compensation can significantly improve the downstream ecological objectives on the basis of meeting the irrigation guarantee rate in the middle reaches; the parallel flower pollination algorithm has significant stability and optimization ability, which is a new method for reservoir optimal operation. The research results not only provide a new idea for the joint operation of surface water and groundwater in arid areas, but also provide important guidance for alleviating the water resources contradiction and improving the utilization efficiency of water resources in Heihe River Basin.

Septic system-groundwater-surface water couplings in waterfront communities contribute to harmful algal blooms in Southwest Florida.

As human population growth has expanded in Southwest Florida, water quality has become degraded with an increased occurrence of harmful algal blooms (HABs). Red tide (Karenia brevis) originating offshore, intensifies in nearshore waters along Florida's Gulf Coast, and blue-green algae (Microcystis spp.) originating in Lake Okeechobee is discharged into the Caloosahatchee River. These HABs could be enhanced by anthropogenic nitrogen (N) and phosphorus (P) from adjacent watersheds. North Fort Myers is a heavily developed, low-lying city on the Caloosahatchee River Estuary serviced by septic systems with documented nutrient and bacterial pollution. To identify sources of pollution within North Fort Myers and determine connections with downstream HABs, this multiyear (2017-2020) study examined septic system- groundwater- surface water couplings through the analysis of water table depth, nutrients (N, P), fecal indicator bacteria (FIB), molecular markers (HF183, GFD, Gull2), chemical tracers (sucralose, pharmaceuticals, herbicides, pesticides), stable isotopes of groundwater (δ15N-NH4, δ15N-NO3) and particulate organic matter (POM; δ15N, δ13C), and POM elemental composition (C:N:P). POM samples were also collected during K. brevis and Microcystis spp. HAB events. Most (>80%) water table depth measurements were too shallow to support septic system functioning (<1.07 m). High concentrations of NH4+ and NOx, up to 1094 μM and 482 μM respectively, were found in groundwater and surface water. δ15N values of groundwater (+4.7‰) were similar to septic effluent (+4.9‰), POM (+4.7‰), and downstream HABs (+4.8 to 6.9‰), indicating a human waste N source. In surface water, FIB were elevated and HF183 was detected, while in groundwater and surface water sucralose, carbamazepine, primidone, and acetaminophen were detected. These data suggest that groundwater and surface water in North Fort Myers are coupled and contaminated by septic system effluent, which is negatively affecting water quality and contributing to the maintenance and intensification of downstream HABs.

Negative Effect of Lambda-cyhalothrin (Insecticide) on Alazani River Fish, Luciobarbus Mursa

Pesticides are complex organic substances that are an important source of water pollution. Using pesticides is one of the important actions for harvest protection. This, however, does not negate the fact that its usage can result to negative consequences as well. The study of toxic action of lambda-cigalotrin (the piretroid of the insecticides which is included in icons, karate, commodore, samurai) on quantitative contents of fatty acids and structural lipids in muscle, gills, liver, and in the brain of fishes in river Alazani was carried out. Based on the actual material, one can conclude that intoxication of the fish tissues with lambda-cyhalotrin processes appear, which stimulates oxidation of free radicals of structural lipids. The peroxides of the initiators of free radicals are formed, which stimulate lipid per oxidation. Exposure to insecticides caused an induction of antioxidant enzyme activities indicating the activation of the insecticides detoxification pathways and the antioxidant defenses. The non-protein sulfhydryl groups increased to 1,75  0,109 compared to the control (1,04  0,123), while the total sulfhydryl groups statistically increased to 39,16  1,44 compared to the control (34,00  1,22 ).This indicates an increase in the concentration of protein and total sulfhydryl groups compared to controls. The study also identified that excess amounts of insecticides in the tissues disrupts the biochemical parameters. These changes may be potentially disruptive for the survivability of fish in natural resources. This fact should thus be taken into consideration when this insecticide is used for pest control in agriculture fields surrounding surface water and ground water resources.

Диагностика состояния почвенного покрова государственного природного заказника «Цимлянский» и процессов эрозии песков

A study of the composition of the soil cover of the territory of the state nature reserve "Tsimlyansky" was conducted in order to track the state of the ecosystem by the main processes of soil formation and indicators of the state of vegetation cover: humus accumulation, the formation of a differentiated profile, projective coverage and the presence of loose sands. The field stage of the study was carried out with the laying of soil sections on sites reflecting the main forms of meso- and microrelief. Samples from each genetic horizon were selected in soil sections for laboratory study of granulometric composition, humus content, nitrogen, phosphorus and potassium content. According to remote sensing data, an assessment of the depth of groundwater occurrence was carried out, a digital relief model and a surface runoff model were built to track probable zones of water erosion of sands. According to the multispectral survey by SWIR-NIR-RED channel synthesis, the areas of loose and loosely anchored sands during the growing season were estimated, the danger of deflationary destruction of the sand massif was estimated. Based on the data obtained, maps of groundwater occurrence, surface runoff and loose sands are constructed. The results of the conducted studies allow us to conclude that the level of resistance to erosion processes is safe for the ecosystem, however, the safety margin of the measures carried out decades ago is approaching a dangerous level, which requires the planting of new protective forests and shrubs to restore the most effective sand retention system. Keywords: GIS, REMOTE SENSING, TSIMLYANSKY NATURE RESERVE, VEGETATION COVER, SOILS, SOIL COVER, SAND MASSIFS

Emerging solute-induced mineralization in Arctic rivers under climate warming

Permafrost degradation under a warming climate is accelerating the hydrological processes in Arctic river basins. However, corresponding changes in river mineralization, riverine solute exports and their potential influencing factors are not fully understood. In this study, we selected six major Arctic rivers (Ob, Yenisei, Lena, Kolyma, Yukon and Mackenzie Rivers) with different permafrost extents, meteorological conditions and hydrological regimes to reveal the changes in river mineralization and riverine solute exports using ArcticGRO sampling data from 2003 to 2019. Our results indicate that solute-induced river mineralization has already been observed in the Lena, Yukon and Mackenzie Rivers during 2003–2019. The annual flux of total dissolved solids (TDS; a key parameter of drinking water quality), calculated by the Load Estimator (LOADEST) program, from these six rivers was approximately 295.24 ± 12.50 Tg, with the Ob, Kolyma and Yukon Rivers exhibiting significant increasing trends (p < 0.05) at rates of 4.38 Tg/10 yr, 1.62 Tg/10 yr and 3.03 Tg/10 yr, respectively. Climate-induced changes in hydrological regimes regulate riverine solute exports, with relatively higher TDS concentrations in the groundwater-dominated winter low-flow season and lower TDS concentrations under the dilution of groundwater by snowmelt spring floods and summer precipitation events. The riverine solute fluxes with higher TDS concentrations (e.g., those of the Yukon and Mackenzie Rivers) increased more rapidly (~0.14 Tg/km3) with changes in river discharge; however, the TDS concentrations were more sensitive to climate warming in continuous permafrost-dominated colder basins (i.e., the Kolyma and Lena River basins) than in other relatively warmer basins. Our results suggest that riverine solute exports are likely affected by permafrost thaw-induced changes in hydrogeological processes, which are tightly associated with increases in active layer thickness and enhanced groundwater discharge to rivers. Under a warming climate, riverine solute exports in Arctic rivers are expected to increase with intensifying groundwater–surface water exchanges.

A multi-criteria approach of assessing groundwater potential, recharge and flow in the transboundary Tuli Karoo Basin

Abstract Quantitative estimates of amount of groundwater resources are required in the transboundary Tuli Karoo Basin to better manage and promote sustainable conjunctive use of the aquifer. Unfortunately, such important data and information are lacking. The aim of this study was to map groundwater potential zones and model groundwater recharge as well as groundwater flow in the Tuli Karoo Basin (12,164 km2) using geospatial techniques. To delineate groundwater potential zones, nine thematic maps of groundwater conditioning factors were computed and weighted using Saaty's Analytical Hierarchy Process (AHP). To validate the groundwater potential map, a Kruskal–Wallis test was performed. Groundwater recharge and groundwater flow direction were estimated in a coupled Geographic Information System (GIS) and modelling environment using the soil–water–balance model (SWB) and British Geological Survey (BGS) groundwater tool, respectively. Results for groundwater potential mapping showed that the area is dominated by high ground water potential which covers about 57.8% (6,915.1 km2) of the basin. The Kruskal–Wallis test showed that the median values of the borehole yields vary significantly between the different groundwater potential zone classes (P-value &amp;lt;0.0001). Estimated groundwater recharge using SWB model showed that the maximum annual potential recharge for the Tuli Karoo Basin was 13.2 mm/year for the 10-year period from 2010 to 2020. Results from the BGS tool for groundwater flow show that the dominant groundwater flow direction is southeast. The results showed that there is no link between groundwater flow direction and surface water flow direction. This study is relevant in water development policy, water-related development aid, community planning and technical decision making for hydrogeologists, catchment managers, water planners and non-specialists alike.