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This article reviews the consequences of man-made burial of river valleys in urban areas. Deep analysis of above-mentioned sources enabled to reveal the consequences of river system destruction in urban areas, located on platforms. Backfilling of the river valleys leads to the following negative changes: surface runoff increases by 200-280%, sediment load increases up to 60-90 m 3 per year by 1 km 2 , suffusion and land subsidence begin to develop within man-made buried valleys (2-3 mm per year). Subsurface flow changes cause progressive groundwater flooding and growing level of water mineralization. Total dissolved solids index grows, these waters become aggressive which results in drainage destruction and damaging of urban infrastructure, such as pipelines and sewerage. Destruction of urban river system leads sharp to the environmental issues: small rivers (including storm drain) accumulate various pollutants and deplete flora and fauna. Karst processes were activated in Moscow a few years after backfilling of the river valleys due to subsurface flow changes.

Extensive deforestation in tropical regions may significantly influence the hydrological cycle. However, subsurface runoff processes in thick soil layers in humid tropical forests are poorly understood; thus, the impact of land-use changes in such regions remains unclear. To understand runoff generation mechanisms in the humid tropics, we monitored groundwater and soil moisture dynamics in a forested hillslope in Sumatra, Indonesia. We also conducted field and laboratory experiments to determine soil hydraulic characteristics and used the results to simulate vertical infiltration and groundwater recharge. Although the soil is categorized as silty clay loam, the high infiltrability and high water retention capacity of the soil enabled infiltration during storm events and recharge to groundwater. Within the 4–5 m thick soil layer at the foot of the hillslope, the shallow groundwater table quickly responded to rainfall and did not drop below a depth of 2–3 m, possibly due to continuous flow contributions from the upslope. Overall, this study demonstrates the importance of subsurface flow and vertical infiltration in thick soil layers in humid tropical regions.

Constructed wetlands as a treatment system are widely explored in different climate conditions and established to be effective in pollution removal from water environment. This study aims to demonstrate the performance of pilot-scale subsurface flow constructed wetland for storm water treatment in Latvia. The catchment basin was located in a farmyard of agricultural area and storm water was collected from the impermeable pavements. Storm water was accumulated in an open pond and periodically pumped above the filter part of the subsurface flow constructed wetland. Grab samples were collected once or twice per month at the inlet and outlet of the treatment system during a period of 73 months from year 2014 to 2020. Water quality parameters as nitrate nitrogen (NO3-N), ammonium nitrogen (NH4–N), total nitrogen (TN), orthophosphate phosphorus (PO4-P), and total phosphorus (TP), total suspended solids (TSS), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were monitored. Water level at the inlet structure was automatically measured and flow rate was calculated based on the Manning equation for partially filled circular pipes. Results showed the reduction of average concentrations for all parameters during the study period. However, in some sampling cases concentrations increased at the outlet of the treatment system and can be explained by influencing factors of farming and maintenance. The treatment efficiency of NO3-N, NH4-N, TN, PO4-P, TP, TSS, BOD5 and COD concentrations was 17 %, 68 %, 55 %, 78 %, 80 %, 57 %, 80 % and 74 %, respectively. The study site demonstrated a potential to improve water quality in the long term.

In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment, the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess, alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province, and the following results were obtained: (1) The source of Hg in subsurface flow zone is mainly caused by mineral processing activities; (2) the subsurface flow zone in the study area is in alkaline environment, and the residual state, iron and manganese oxidation state, strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment; mercury in river alluvial or diluvial strata is mainly concentrated in silt, tailings and clayey silt soil layer, and mercury has certain stability, and the form of mercury in loess is easier to transform than the other two media; (3) under the flooding condition, most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed, and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection; (4) infiltration at the flood level accelerates the migration of pollutants to the ground; (5) the soil in the undercurrent zone is overloaded and has seriously exceeded the standard. Although the groundwater monitoring results are safe this time, relevant enterprises or departments should continue to pay attention to improving the gold extraction process, especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes, and intensify efforts to solve the geological environmental problems of mines left over from history. At present, the occurrence form of mercury in the undercurrent zone is relatively stable, but the water and soil layers have been polluted. The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links. The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.

The abundance of bacterioneuston and bacterioplankton and their taxonomic composition were determined with the fluorescence in situ hybridization (FISH) method in the harbor channel in Ustka. Among bacteria inhabiting the surface microlayer and subsurface water two phylogenetic groups dominated: Gammaproteobacteria and Cytophaga-Flavobacterium. The abundance of bacterial taxonomic groups in the water of the studied channel showed typical ranking, i.e., Gammaproteobacteria > Cytophaga-Flavobacterium > Marine alpha cluster > Pseudomonas > Vibrio. Total prokaryotic cell differed along the vertical and horizontal profiles. Similar taxonomic composition of bacterioneuston and bacterioplankton in both studied profiles were noted. All studied taxonomic groups occurred more often in the surface microlayer than subsurface water.

This study aimed to assess the impact of the Nile flood with special reference to turbidity on the food chain in Lake Nasser water as one of the largest man-made lakes in Africa before the flood (BF) and after the flood (AF) seasons. To achieve that aim, subsurface water samples were collected from 11 sampling stations along the lake before and after the flood for analyzing the water turbidity, total suspended solids, and total phosphorus, as well as chlorophyll-a and zooplankton to represent the food chain in the lake. Results showed an increase in water turbidity after the flood than that before the flood. Total suspended solids concentration displayed a similar trend as water turbidity. Chlorophyll-a concentration increased in AF all over the lake except at the entrance of the lake, as compared to the BF season. Zooplankton count was represented by copepods, cladocerans, and rotifers with the dominance of copepods in AF and rotifers in BF. The density of zooplankton was higher in the AF than the BF season. The negative impact of flood turbidity had appeared on crustacean organisms.

This study aimed to provide relevant knowledge about the dynamics of the hydrological parameters in the river-estuary continuum of the Wouri-Nkam river estuary for a sustainable management program. The hydrological parameters were recorded in eleven stations spanned out on the basis of population density and human activities. Water quality parameters (Temperature, salinity, dissolved oxygen, pH, Total dissolved solutes, Redox potential and conductivity) were collected in subsurface water using a multiple parameter. Surface currents and morphometric (depth and width) parameters were recorded using a drifter, sonar depth and GPS. The field measurements took placed between 18/05/2019 to 08/09/2020 and were divided into six (06) cruises. The data were later subjected to an analysis of variance (ANOVA) and Principle Component Analysis using XLSTAT 2017 (2.7 version) software. Results obtained revealed that, the water quality parameters were spatially more stable notsignficant at (df = 9, p 0.05) with a relatively low temperature (25.5°C - 27°C) during the wet period. The limit of the frontal zone extended to S5 (Bonalokan, 8.25 km from S1) during the snapshot of the dry period, spring phase and flood tide conditions. Inversely, during wet period, this extension reduced to S1 (Bridge) and relatively increases slightly to S3 (Bonangang) during the neap phase and ebb tides of this season. This result revealed a change in the axial gradient of about eight (08) and four (04) kilometers during the seasonal and tidal scales (lunar and diurnal periods) respectively. These changes were also accompanied by changes in the water quality signatures, that may affect the fishery distribution and compositions. However, futures studies to buttress the results of this investigation should focus on longer time series sampling methods and model developments.

The Northeast Pacific coastal ocean, as a typical river-influenced coastal upwelling system, is characterized by significant variability of sea surface partial pressure of carbon dioxide (pCO2, 1000 μatm). This study reviewed the pCO2 variability and its underlying controlling mechanism in this highly dynamic region by bringing together previous scientific findings and historical data. The large pCO2 variability reflects the complex interactions between physical processes (riverine input and coastal upwelling) and the biological responses to the nutrient transportation associated with these physical processes, while temperature and air-sea gas exchange play a minor role in affecting pCO2. Both the river water and upwelled subsurface water are characterized by higher concentrations of pCO2 and nutrients when compared to the coastal surface water. The presence of high chlorophyll-a and low pCO2 in river plumes and areas adjacent to upwelling locations showed the intense biological CO2 uptake. The influences of riverine input and coastal upwelling thus mainly depend on the competing effect of high background pCO2 of river water and upwelled subsurface water vs. the biological dropdown of pCO2 resulting from the riverine- and upwelling-associated nutrient supplies. The strength of upwelling-favorable wind plays an important role in the pCO2 variability by affecting the intensity of coastal upwelling, with stronger wind speed causing more intense upwelling. The long-term pCO2 increasing rate in the Northeast Pacific coast is observed to be lower than that in the North Pacific open ocean.

A new patented constructed wetlands treatment technology for enhanced nutrients reduction has been developed by Tennessee Valley Authority. This new treatment technology is known as Reciprocating Flow Constructor Wetland (RFCW) through increasing oxygen content in the treatment processes. The RFCW has a process of operating two adjacent subsurface flow gravel beds by alternately draining and filling the wastewater on a recurrent basis to achieve tertiary levels of wastewater treatment. In Egypt, A pilot-scale RFCW was built near Lake Manzala as a demonstration of low cost treatment technology to treat a portion of Bahr El-Baqar drain wastewater that carries drainage water contains domestic and industrial pollution loads. The pilot wetland consists of one sedimentation basin followed by two subsurface flow cells working in a fill-empty sequence mechanism. The treatment capacity is 100 m per day. Treatment detention time is 4 days including 2 days in the gravel bed RFCW cells. Objectives of this paper are to describe operational flow inside the alternate cells, and to evaluate the treatment performance of reciprocating wetland for such polluted drainage water and to estimate removal rate constants (K) of the treated pollutants applying mixed flow reactor model. Water samples were collected from both influent and effluent wetland cells. Samples were analyzed to measure concentrations and loads of DO, BOD, TSS, NH4-N, NO3-N, TP, Fe, and FC. Results showed that RFCW managed to polish pollutants of drainage influent especially ammonia and nitrates reaching a limit which it could be used in a safe manner for the agricultural purpose or dumping it into Lake Manzala without negative impacts on its ecosystem.

We measured the daily evapotranspiration on a horizontal sub-surface flow constructed wetland in Hódmezővásárhely, Hungary. The main focus of our research was the seasonality of evapotranspiration in this CW. We measured the water balance of the CW and searched days when no precipitation, no inlet or outlet impacted on the water balance of the constructed wetland, only the evapotranspiration. had impact on the water balance. The results show that in spring the evapotranspiration rates were between 18-42,6 mm/day, in summer 12,3-42,3 mm/ day and in autumn the values were 13,6-22,7 mm/day. The highest hourly evapotranspiration was 16,3% of the daily evapotranspiration. This value was 415 % of the average, hourly hydraulic load that can significantly affects on the effluent concentration. The results also show the morning and evening condensation which has two main effects. On the other hand, the water balance of the CW is increased, which results the decrease of the concentration of wastewater.

In recent years, groundwater pumping has increased for domestic, industrial, and irrigation use in the Modjo River catchment. Understanding changes in groundwater levels is crucial for the sustainable use and management of aquifer. This study investigates the groundwater flow system and aquifer response to increased groundwater pumping and reduced recharge using the calibrated steady-state groundwater level and budget as a baseline. The groundwater flow corresponds to the direction of the Modjo River flow, following the topographic gradient. The simulated groundwater budget indicates that recharge from precipitation and surface water (crater lakes and river) are the main inflow to the aquifer, while the outflow from the aquifer is due to groundwater pumping, natural subsurface flow to downstream area, and base flow. Analysis of the different scenarios reveals that both an increase in well pumping and a decline in recharge resulted in a decrease of the base flow to Bishoftu crater lakes and Mojo River, and to the downstream subsurface flow. In conclusion, increasing human demand for groundwater and variability in recharge will affect groundwater contribution to surface water and ultimately will be a source of concern in the future for both environmental flows and groundwater management.

Bank filtration is considered to improve water quality through microbially mediated degradation of pollutants and is suitable for waterworks to increase their production. In particular, aquifer temperatures and oxygen supply have a great impact on many microbial processes. To investigate the temporal and spatial behavior of selected organic micropollutants during bank filtration in dependence of relevant biogeochemical conditions, we have set up a 2D reactive transport model using MODFLOW and PHT3D under the user interface ORTI3D. The considered 160-m-long transect ranges from the surface water to a groundwater extraction well of the adjacent waterworks. For this purpose, water levels, temperatures, and chemical parameters were regularly measured in the surface water and groundwater observation wells over one and a half years. To simulate the effect of seasonal temperature variations on microbial mediated degradation, we applied an empirical temperature factor, which yields a strong reduction of the degradation rate at groundwater temperatures below 11 °C. Except for acesulfame, the considered organic micropollutants are substantially degraded along their subsurface flow paths with maximum degradation rates in the range of 10−6 mol L−1 s−1. Preferential biodegradation of phenazone, diclofenac, and valsartan was found under oxic conditions, whereas carbamazepine and sulfamethoxazole were degraded under anoxic conditions. This study highlights the influence of seasonal variations in oxygen supply and temperature on the fate of organic micropollutants in surface water infiltrating into an aquifer.

This paper offers a novel application of our model worked out in Maple environment to help understand the very complex transport processes in horizontal subsurface flow constructed wetland with coarse gravel (HSFCW-C). We made tracer measurements: Inside a constructed wetland, we had 9 sample points, and samples were taken from each point at two depths. Our model is a divided convective-dispersive transport (D-CDT) model which makes a fitted response curve from the sum of two separate CDT curves showing the contributions of the main and side streams. Analytical solutions of CDT curves are inverse Gaussian distribution functions. This model was fitted onto inner points of the measurements to demonstrate that the model gives better fitting to the inner points than the commonly used convective-dispersive transport model. The importance of this new application of the model is that it can resemble transport processes in these constructed wetlands more precisely than the regularly used convective-dispersive transport (CDT) model. The model allows for calculations of velocity and dispersion coefficients. The results showed that this model gave differences of 4–99% (of velocity) and 2–474% (of dispersion coefficient) compared with the CDT model and values were closer to actual hydraulic behavior. The results also demonstrated the main flow path in the system.

Acid sulfate soils (ASSs) are naturally formed soils or sediments that are produced under waterlogged and poorly drained conditions. The sulfides can move to the surface water and into subsurface water and cause loss of nutrients in the soil and destroy the soil structure. To perform effective management of the ASSs located above and under the groundwater table, the unsaturated characteristics of ASSs before and after neutralization treatments should be investigated. An ASS was sampled from the natural soil layer around Ilkwang mine in Busan, South Korea, and CaCO3, which is a neutralizer, and polyacrylamide (PAM) which is a soil stabilizer, were mixed with the ASS in the neutralization treatment. The soil-water characteristics curves (SWCCs) and hydraulic conductivity functions (HCFs) of the drying-wetting processes of the ASS before and after the neutralization treatment were measured and assessed using the van Genuchten model. According to the assessment results of the SWCCs and HCFs, the matric suction of the ASS after the treatment was smaller than that before the treatment at the same volumetric water content (VWC). Additionally, the hydraulic conductivity of the ASS after treatment was larger than that before treatment at the same effective degree of saturation because the effective particle size of the ASS increased and the pore size among particles increased due to soil aggregation. It was confirmed that the neutralization treatment improved the hydrological properties of the ASS and the ASS after treatment may be utilized as sound materials for various fields.

A model for the subsurface flow and associated oxygen transfer induced by surface flow and slip velocity is presented in a gravel bed river. The shear velocity (U *) and hydraulic conductivity (K) ...

Groundwater and subsurface water have important roles in river ecosystems: e.g., stabilizing flow regime and water temperature, supplying nutrients, and increasing biodiversity. However, detection of springs and quantitative estimation of groundwater contribution to the surface water ecosystems are not easy in the field. Although some indirect measurements combing simulations and models have been widely used to estimate the groundwater flow, they require certain assumptions, thus it is rather difficult to estimate the discharge of groundwater on a local scale. Direct field-scale measurement of groundwater flow is also difficult particularly for researches of ecology and environmental science. In this study, we present biological indicators of benthic invertebrates to evaluate the contribution of groundwater to surface water bodies. Because the benthic invertebrates show distribution patterns reflecting habitat scale environmental conditions in a sensitive manner, they are expected to serve as a biological indicator of groundwater spring sites. We collected data of benthic invertebrates from literature in a global scale and additional field research in Japan. By analyzing their taxonomic features and biological habits, we identified spring indicator taxa of benthic invertebrates based on the degree of dependency to groundwater environment. A total of 1,448 aquatic invertebrate species representing 58 orders were found from 249 research sites. The spring indicators were identified as spring dependent species including groundwater species (Stygobites and Stygophiles), cave species (Troglobites and Troglophile), and stenothermal species. Considering the geographical distribution patterns of the spring indicator taxa, stenothermal species were classified into "cold stenothermal species" which evolutionarily originate in more boreal regions and "warm stenothermal species" derived from more tropical regions. Ecological interpretation of these stenothermal species was discussed in relation to climatic zones and altitude of the basin concerned. Based on the variations of spring contribution into river ecosystems suggested by the spring indicator species, we proposed an application procedure of the spring indicators for environmental assessment and nature conservation works in river management.

Hydrological models of simulating the process of runoff generation play a pivotal role to predict the dynamic hydrological fluxes and states. In order to describe the process of runoff generation, three mechanisms (i.e., Dunne, Horton and Subsurface flow mechanisms) have been developed and widely applied in hydrological model. Due to the heterogeneity of underlying surface conditions (e.g., soil properties, topography and antecedent soil moisture) and meteorological factors, a complex runoff generation process pattern formed by more than one mechanism can often be found at different spatiotemporal scales. A novel hybrid runoff generation mechanism has been proposed to simultaneously incorporate Horton, Dunne and Subsurface flow mechanisms and describe the dynamic processes of runoff generation. And a modified variable infiltration capacity (VIC) model based on this novel hybrid runoff generation mechanism has been developed to simulate more authentic rainfall-runoff generation processes. In order to test the performance of our modified VIC model, the upper reach of Hanjiang River basin with varying climate conditions is selected as a case study. Results show that the modified VIC model not only performs as well as the benchmark model with respect to streamflow simulation, but also the complex dynamic process of rainfall-runoff generation can be clearly described based on the hybrid mechanism. Our study reinforces model development on the authentic processes of rainfall-runoff generation in distributed hydrological models.

We worked out a method in Maple environment to help understand the difficult transport processes in horizontal subsurface flow constructed wetlands filled with coarse gravel (HSFCW-C). With this process, the measured tracer results of the inner points of a HSFCW-C can be fitted more accurately than with the conventionally used distribution functions (Gaussian, Lognormal, Fick (Inverse Gaussian) and Gamma). This research outcome only applies for planted HSFCW-Cs. The outcome of the analysis shows that conventional solutions completely stirred series tank reactor (CSTR) model and convection-dispersion transport (CDT) model do not describe the internal transport processes with sufficient accuracy. This study may help us develop better process descriptions of very complex transport processes in HSFCW-Cs. Our results also revealed that the tracer response curves of planted HSFCW-C conservative inner points can be fitted well with Frechet distribution only if the response curve has one peak.

The purpose of this study was to examine the most suitable groundwater vulnerability method and formulate karst groundwater vulnerability management based on the distribution of the resulting vulnerability class. The most suitable groundwater vulnerability method was selected with a tracer test as well as by analysing its compatibility with the conditions of the study site, distribution of the vulnerability classes, spatial autocorrelation and comparison with other studies. The study was conducted on Guntur Spring, which is one of the tropical karst springs located in the western region of Gunungsewu Karst, Java Island, Indonesia. This perennial spring is used by approximately 1,000 people. This spring has the potential to be polluted due to the characteristics of the catchment area, which typify the connectivity between the surface and subsurface flow systems. The management of the Guntur Spring catchment was based on the distribution of vulnerability classes that are also adapted to the geomorphological, hydrogeological and land-use conditions. The analysis showed that EPIK is the most suitable method compared with COP, PI and PaPRIKa. The recommended management of the karst groundwater vulnerability included: (1) creating a protective structure at swallow holes; (2) reforestation and erosion management of thin soils on the crest of the karst hill; (3) addition of multilayer vegetation coverage to the upper, middle and bottom layers of the cockpit karst; (4) land-use and fertiliser limitations in the karst valley; and (5) restrictions on land use that produces pollutants around the lineaments, underground rivers and recharge points.

The objective of this study was to evaluate the influence of stoloniferous and fasciculated root systems, of Tifton 85 and vetiver grass respectively, on pollutant removal for primary treatment of sewage in horizontal subsurface flow constructed wetlands (HSSF-CWs). For this, three HSSF-CWs measuring 4 m × 1 m × 0.25 m, filling with gneiss gravel # 0 (D60 of 7.0 mm and 48.4% porosity) as substrate, were used. One unit was cultivated with Tifton 85 grass (HSSFT-CW), one with vetiver grass (HSSFV-CW) and one remained uncultivated (HSSFC-CW) as a control. Sewage was applied at a flow rate of 0.53–0.80 m3 d−1, corresponding to an organic loading rate of approximately 350 kg ha−1 d−1 (biochemical oxygen demand – BOD), which resulted in a hydraulic retention time of 0.6–0.9 day. The HSSFV-CW was more efficient than the HSSFC-CW in removing dissolved solids (measured as electrical conductivity) and reducing the total suspended solids (TSS), BOD5, turbidity and sodium concentration, while the HSSFT-CW was not superior in any way. The results indicate that cultivation of vetiver grass provided increased efficiency for removing pollutants from sewage when compared with Tifton 85-grass, in the HSSF-CW.

Rainfall–runoff modelling has always been of great importance in hydrology. Recently, the Event-Based Approach for Small and Ungauged Basins (EBA4SUB) model, based on the instantaneous unit hydrogr...

Multi-year droughts in Mediterranean climates may shift the water balance, that is, the partitioning rule of precipitation across runoff, evapotranspiration, and sub-surface storage. Mechanisms causing these shifts remain largely unknown and are not well represented in hydrologic models. Focusing on measurements from the headwaters of California's Feather River, we found that also in these mixed rain–snow Mediterranean basins a lower fraction of precipitation was partitioned to runoff during multi-year droughts compared to non-drought years. This shift in the precipitation–runoff relationship was larger in the surface-runoff-dominated than subsurface-flow-dominated headwaters (−39 % vs. −18 % decline of runoff, respectively, for a representative precipitation amount). The predictive skill of the Precipitation Runoff Modeling System (PRMS) hydrologic model in these basins decreased during droughts, with evapotranspiration (ET) being the only water-balance component besides runoff for which the drop in predictive skill during drought vs. non-drought years was statistically significant. In particular, the model underestimated the response time required by ET to adjust to interannual climate variability, which we define as climate elasticity of ET. Differences between simulated and data-driven estimates of ET were well correlated with accompanying data-driven estimates of changes in sub-surface storage (ΔS, r=0.78). This correlation points to shifts in precipitation–runoff relationships being evidence of a hysteretic response of the water budget to climate elasticity of ET during and after multi-year droughts. This hysteresis is caused by carryover storage offsetting precipitation deficit during the initial drought period, followed by vegetation mortality when storage is depleted and subsequent post-drought vegetation expansion. Our results point to a general improvement in hydrologic predictions across drought and recovery cycles by including the climate elasticity of ET and better accounting for actual subsurface water storage in not only soil, but also deeper regolith that stores water accessible to roots. This can be done by explicitly parametrizing carryover storage and feedback mechanisms capturing vegetation response to atmospheric demand for moisture.

Research has been carried out to identify the presence of subsurface water in Selulung Village, Kintamani District, Bangli Regency using 2D geoelectric methods. The work process of this research is the first to collect data directly by using a geoelectric device with Wenner configuration. Electric currents are injected from the surface to the subsurface through the current electrodes which are put on the earth's surface. The collected data is then processed using the Res2Din software version 3.71.118. The software results in the form of 2D images are direct lateral images of subsurface structures. From the three trajectories identified, namely at the coordinates 8°12'18.7"S 115°16'08.3"E the lowest resistivity value was 178 Ohm m with a depth of 10 m which was thought to be a rock layer with surface water content. On line 2 at coordinates 8°12'16.1"S 115°16'09.7"E the resistivity value is 6 ohm.m up to 660,000 ohm.m, the maximum depth obtained is 24 m. This line is thought to be a water-bearing layer because the value of resistance is low. Line 3 which is in the coordinates 8°12'16.3"S 115°15'50.0"E the distribution of resistivity values varies from 42 - 9,400 Ohm m.

This review presented a detailed re-assessment of the hydrogeology and hydrochemistry of the Tropical Anambra Basin. It identified and discussed the major geological formations and their groundwater potentials. The geological examination showed that the Ajali Formation is confined in places forming an artesian condition; the potentials of this aquifer decline in the western basin due to a decrease in thickness. The sandstone associates of the Nsukka Formation are aquiferous and have produced high-pressure artesian boreholes along the Oji River. The Imo Shale is characterized by permeability stability all over much of the intermediate unit. The Bende-Ameki aquifer has a lesser amount of groundwater when equated to other formations; the geologic characteristics do not produce favorable hydrogeological conditions for groundwater occurrence. The stratigraphical and structural framework suggested the presence of an efficient throughflow in the basin. Based on physical and chemical parameters of water quality, the basin holds water of acceptable quality. While there are considerable investigations on the hydrogeology and hydrochemistry, studies are short of analysis of the hydrogeochemical evolution of groundwater, water quality index, heavy metals pollution index as well as total hazard quotient. Suitability of groundwater based on agricultural water quality indices (e.g. SAR) is also salient. Therefore, future studies should address these owing to increasing dependence on groundwater.

Municipal wastewater treatment through horizontal subsurface flow (HSSE) constructed wetlands using three different treatment media (gravel, pieces of plastic pipes, and shredded tire rubber chips) were investigated in Samaha wastewater treatment plant, Dakahlia, Egypt. This study focused on the wetland set up stage during the first months of wetland operation. In this stage media porosity, bacterial biofilm, and plants roots growth were in progress and it was prior to the operational steady state stage. Objectives of this paper are to study the change in media porosity of HSSF wetland cells, to evaluate the use of different bed media on BOD treatment and to study the relationship between wetland hydraulic properties and pollutant removal rates during set up stage. The results showed that after 180 days of operation the wetland cells had reached steady porosity. Also, plastic cell gave more BOD reduction than gravel and rubber cells by average values of 4.83% and 8.66% respectively.

High concentration of nitrogen and phosphorus (above 20 and 1.5 mg/L, respectively, for TN and TP) and low ratio of nitrogen to phosphorus (10–15 for N/P) in secondary effluent of cities in China a...

Ground movement is common around hilly areas; as such, there is a need to investigate the activities of the ground surface and subsurface of such regions. This research presents an application of the Permanent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique and electrical resistivity (ER) method for the measurement of ground deformations and investigation of the subsurface features, respectively, at Paya Terubong, Penang Island. The PS-InSAR is an instrument for detecting patterns of deformation over a wide region, while the ER approach is used to image subsurface characteristics and measure the resistivity of the rock formation. Satellite data obtained from Sentinel-1A (S-1A) were used to detect some active ground deformation zones. The velocity of − 41 mm/Yr was discovered along the line of sight (LOS) of the system, indicating subsidence. An ER survey was performed at the topsoil within 5 m depth based on the ground deformation patterns detected through the InSAR technique. Two-dimensional (2-D) resistivity lines were laid using the ABEM SAS4000 Terameter and a dipole–dipole array with an electrode spacing of 2.5 m. The areas with low values of resistivity ranging between 0 and 20 Ωm were classified as saturated zones. The efflux and influx of subsurface water when the layers of rocks are lubricated and downcutting of steep slopes are among the suspected causes of deformation. The application of the two techniques has improved the understanding of both the surface and subsurface mechanisms, reduced variation in the results, and allowed the investigation of active landslide areas.