Changes In Groundwater Table Research Articles

Groundwater-table-induced slope displacement analyses using different failure criteria

A force-equilibrium-based finite displacement method (FFDM) incorporating Mohr-Coulomb (M-C) and Hoek-Brown (H-B) failure criteria is used to compute displacements of a monitored slope undergoing rainfall-induced groundwater table (GWT) fluctuations. The analytical method consists of back-calculating strength and displacement parameters using recorded displacements and groundwater table (GWT) in the 1st event of a series of rainfall-induced GWT changes and predicting slope displacements for other events of GWT changes. Results of analyses for the studied slope indicate that (1) despite various sets of back-calculated strength and displacement parameters are obtained, the accuracy of slope displacement prediction is not affected by using various sets of back-calculated parameters; (2) the accuracy of slope displacement prediction is not affected by the use of different failure criteria (M-C or H-B). To simulate a sliding with variable displacements along the slip surface, a displacement diagram associated with an operational dilatancy angle (ψ) is used, i.e., a negative value of ψ is selected to approximate a sliding mass undergoing a volume contraction. Results of a comparative study preliminarily shows good agreement between the calculated and the measured displacements of the slope. However, further validation for this technique using more observed data are necessary.

Mechanical Behaviour of Self Compacting Concrete by using M-sand & Rice Husk ash

Rice husk ash (RHA) is an agricultural based pozzolanic material, which contains high amount of silica content. This experimental research was conducted on Self Compaction Concrete (SCC), to generate an economical concrete by using Manufactured Sand (M-sand) and Rice Husk Ash. Natural River sand usage is damaging the river beds, causing the drastic changes in ground water table and cost of river sand increasing day by day. To overcome this problems manufactured sand is used in SCC production. Rice husk Ash is very cheaper when compared to the Cement. It is extracted from Rice Husk which is a waste of Agricultural product. This material can be useful to generate a sustainable construction material. This paper presents the experimental results on development of mechanical properties of SCC with M-sand and Rice Husk Ash. Experiment conducted on 6 different mixes. i.e Partial Replacement with RHA (0%, 5%, 10%, 15%, 20%, 25%). For each mix Fresh properties (Slump flow & L-Box Test) & mechanical properties (Compressive strength, Split Tensile strength and Flexural strength) for 7days, 28days and 60days along with Density comparisons are compared.

Review of time-lapse microgravity correction due to shallow groundwater variation

Microgravity surveys can be applied for reservoir monitoring, such as monitoring of hydrocarbon or geothermal reservoirs. One factor that needs to be corrected from gravity data in reservoir monitoring is the gravity signal due to shallow groundwater variation. The correction due to shallow groundwater effect shall be calculated from groundwater change, in this case can be measured from groundwater table change. So far, correction due to shallow groundwater variation in microgravity data is calculated against the influence of groundwater mass change in the saturated zone only, while the change of mass of groundwater in the unsaturated zone is ignored, thus giving an over-estimated correction result. The purpose of this paper is to review time-lapse microgravity correction due to shallow groundwater variation by including the influence of groundwater mass variation in the unsaturated zone. This review includes a case study using three-point piezometer groundwater data. The correction due to groundwater mass variation in the unsaturated zone is obtained by calculating the difference between the total water content at two measurements over a certain time interval. The calculation of total moisture content in the unsaturated zone is based on a soil-water retention curve that describes the relationship between moisture content and pore pressure. Considering the effect of water mass in the unsaturated zone, the total correction due to shallow groundwater variation has a smaller range, about 35% to 50% compared to the correction that only considers the effect of water mass in the saturated zone alone.

Efficient allocation of agricultural land and water resources for soil environment protection using a mixed optimization-simulation approach under uncertainty

This study proposes an optimization-simulation approach for simultaneously determining crop patterns and allocating irrigation water to improve soil environment. The approach incorporates an optimization model (a Chance-Constrained Programming (CCP) based multi-objective non-linear programming) integrated with a carbon footprint (CF) model and irrigation water use efficiency (IWUE) index, a soil water balance model and a groundwater dynamics model. The output of the optimization model constitutes the input to the soil water balance model which is calculated based on soil water content from soil samples representing the basin under study, and the resulting output is the input to the groundwater dynamics model. The output of the groundwater dynamics model is examined by whether the optimal results give rise to soil salinization. The proposed approach has advantages in addressing the tradeoffs of land and water resources for different crops in irrigation districts to reduce soil carbon emissions and improve land and water resources allocation efficiency, dynamically reflecting water transformation among precipitation, surface water, soil water and groundwater, and dealing with nonlinearity and uncertainties. The approach was applied to identify optimal land and water resources allocation schemes in the oasis of Heihe River basin, northwest China. Results demonstrated that in the studied area, soil carbon emissions decreased and water use efficiency increased by the simultaneous allocation of the interactive agricultural land and water resources in space and time. Choosing the violation probabilities in the range of 0.05 and 0.1 might be more beneficial to the comprehensive benefits of the contradictory objectives (i.e. reducing soil carbon emissions and increasing irrigation water use efficiency), because during this range the value of IWUE tended to be the largest and the value of CF was beginning to stabilize. From the perspective of spatial distribution, the value of CF showed an increasing trend from northwest to southeast, while the changes of groundwater table in the southern part were higher than in the northern part of the oasis. As the main limiting factor, increasing water availability led to an increase of cultivated land within a certain range, which significantly affected soil environment, leading to the necessity to contribute towards the efficient utilization of irrigation water resources and field activities to reduce soil pollution. Therefore, the proposed modelling framework can help to comprehensively manage agricultural land and water resources under complexity in an efficient and environmental-friendly way, and thus promote soil environment protection.

Effects of saturation degrees, freezing-thawing, and curing on geotechnical properties of lime and lime-cement concretes

There are very limited researches carried out to investigate the influence of saturation degrees, freezing-thawing, and curing times on geotechnical properties of lime concrete (LC) and lime-cement concrete (LCC) due to the capillary action and changes in groundwater table. Subsequently, the primary goal of this research is to investigate the influence of these parameters on mechanical properties of LC and LCC using unconfined compression tests, namely uniaxial compressive strength (UCS), stress-strain behavior, deformability index (ID), secant modulus (ES), failure strain, bulk modulus (K), resilient modulus (MR), brittleness index (IB), and shear modulus (G). At first, the mechanical and chemical characteristics of the utilized materials were measured. Then, samples were made with an optimal amount of cement, lime, coarse-grained soil, fine-grained soil, and water. The samples were then exposed to saturation points extending from 0 to 100% after 14, 28, 45 and 60 curing days. Then, to consider the effect of amount of saturation on the mechanical properties, UCS tests were performed on some of the samples. Other LCC specimens were exposed to freezing-thawing conditions to consider the effect of this phenomenon on the mechanical properties as well. The results of more than 250 UCS tests demonstrated that the curing times significantly affected the strength of LC and LCC specimens. Moreover, it is not ideal and logical to utilize LC and LC columns at a profundity underneath or near the groundwater level, though it is reasonable to adopt LCC and LCC columns at a profundity beneath or near the groundwater level because of the immaterial effect of degrees of saturation on LCC. In addition, this study showed that extending the curing period and diminishing the saturation degree would increase the strength and mechanical properties of the LCC specimens. The results of freezing-thawing demonstrated a negligible increase in the strength of the LCC when the thawing process preceded the freezing process. However, the effect of freeze-thaw cycles on the strength properties of LCC may mostly be neglected.

Spatiotemporal LULC change impacts on groundwater table in Jhargram, West Bengal, India

Groundwater resources are the significant factor for maintaining life. The land use/cover (LULC) change and its effect on the groundwater table would enhanced land use and groundwater management for arid areas. This paper proposes a technique to LULC effects on the groundwater table. LULC extract based on time-series Landsat imagery (1988, 1993, 1998, 2003, 2007, 2013 and 2017) and its effect on the groundwater table. SVM algorithm used for classification of LULC features and its higher accuracy. In the study area, groundwater data (2001–2012) used for groundwater table change analysis. The result showed that 1.03 mbgl (Metres Below Ground Level) groundwater decreased in the study area. Analysis of the time-series climate data (1988–2014) based on the study area shows apex’s for maximum temperature increased between 0.2 and 0.8 °C and 0.3 to 1.5 °C for minimum apexes. At the same time, analysis of historical rainfall data indicated that rainfall decreased by 10 mm, respectively during the years 1988–2014. The classification results showed that the SVM algorithm overall accuracy of 86.67% and the kappa coefficient of 0.82. The relationships among LULC and, climate, groundwater change values showed both positive and negative correlations. This paper highlighted the LULC change effect on the groundwater table change in arid areas.

Groundwater Flow Modeling in the Malioboro, Yogyakarta, Indonesia

Malioboro is a famous tourism area in Yogyakarta City, in which there aremany hotels and increases every years and this follows by the increasing needs of fresh water taken from underlying groundwater. The decreasing of groundwater table become a great issue on this area, therefore the objective of the research is to predict groundwater table change in the next 10 years due to increase abstraction of groundwater. To answer the mentioned objectives, field observation of dug wells and collection of secondary data of log bores also calculation of recharge and water abstraction are used to understand and build the conceptual model of local groundwater system. The prediction is done by conducting simulation on a numerical groundwater model by using MODFLOW. The local groundwater system consists of two aquifer layers; upper aquifer and lower aquifer which separated incompletely by clay layer. Simulation is conducting by distributing the groundwater pumping for domestic and non-domestic utilization by dug wells in the upper aquifer, whereas deep wells non-domestic utilization are applied only in the lower aquifer. Simulations are conducted twice for the recent day and the next ten years predictionof groundwater abstraction. In the case of groundwater abstraction in the next tenyears, dug wells abstraction and deep wells pumping are setting to 4727 m3/day and 1648 m3/day, respectively. The groundwater pumping rates is representing increase of groundwater withdrawal of users in the range only between 0.2–1.2 % per year compare to the recent condition. The simulation reveals change occur on groundwater table depth and pattern. In average, the groundwater table will decrease of about 0.25 meter.

Impact of different cropping systems and irrigation schedules on evapotranspiration, grain yield and groundwater level in the North China Plain

Water shortage is the most limiting factors for the crop production in the North China Plain (NCP). The alternative cropping systems and the water-saving irrigation schedules are the main measures to reduce the groundwater level decline. In this study, APSIM model was used to simulate the effects of four different cropping systems (winter wheat and summer maize cropping system (WW-SM); winter wheat cropping system (WW); summer maize cropping system (SM); winter wheat –summer maize – spring maize cropping systems (WW-SM-sM)) under four different irrigation schedules (normal irrigation (NI); critical irrigation (CI); minimum irrigation (MI); and rain-fed (RF)) on evapotranspiration (ET), water use efficiency (WUE) groundwater table level and crop water productivities in the NCP. Results showed that the WW-SM cropping system had the higher grain yield and ET under NI, CI, MI, and RF conditions. Grain yield reduction (GYR) was decreased with the irrigation amount decreased for the WW cropping system, SM cropping system, and WW-SM-Sm cropping systems which ranged from 21.59% to 48.11%, from 16.71% to 46.93%, from 15.82% to 43.92%, and from 5.09% to 27.22% under the NI, CI, MI and RF irrigation schedules, respectively. For WUE and the economic water use efficiency (WUEe), WW-SM and WW-SM-sM had the higher value, WW and SM had the lower value. The differences for the different cropping systems were mostly caused by the grain yield and the soil evaporation. Meanwhile, the water-saving irrigation schedules and cropping systems both could reduce the groundwater table decline compared to that under normal irrigation and traditional cropping system. There all had the significant impact on groundwater table changes for both the irrigation schedules and cropping systems. However, water restriction will lead to crop yield reduction and water saving depending on the chosen alternative cropping systems and irrigation schedules. Results strongly suggest that the critical irrigation and WW-SM-sM cropping system could mitigate the groundwater over-exploitation and ensure the food safety in the NCP.

Semi-seasonal groundwater forecast using multiple data-driven models in an irrigated cropland

Abstract In agricultural areas where groundwater is the main water supply for irrigation, forecasts of the water table are key to optimal water management. However, water management can be constrained by semiseasonal to seasonal forecast. The objective is to create an ensemble of water table one- to five-month lead-time forecasts based on multiple data-driven models (DDMs). We hypothesize that data-driven modeling capabilities (e.g., random forests, support vector machines, artificial neural networks (ANNs), extreme learning machines, and genetic programming) will improve naïve and autoregressive simulations of groundwater tables. An input variable selection method was used to carry the maximum information in the input (precipitation, crop water demand, changes in groundwater table, snowmelt, and evapotranspiration) and output relationship for the DDMs. Five DDMs were implemented to forecast groundwater tables in an unconfined aquifer in the Northern High Plains (Nebraska, USA). Root mean squared error (RMSE) and Nash–Sutcliffe efficiency index were used to evaluate the skill of the model and three hydrologic regimes were determined statistically as high, mid, and low groundwater table levels. Additionally, varying storage regimes were used to construct rising and falling limbs in the tested well. Results show that all models outperform the baseline for all the lead times, ANNs being the best of all.

Spatiotemporal analysis of bacterial biomass and activity to understand surface and groundwater interactions in a highly dynamic riverbank filtration system

Characterization of surface water – groundwater interaction in riverbank filtration (RBF) systems is of decisive importance to drinking water utilities due to the increasing microbial and chemical contamination of surface waters. These interactions are commonly assessed by monitoring changes in chemical water quality, but this might not be indicative for microbial contamination. The hydrological dynamics of the infiltrating river can influence these interactions, but seasonal temperature fluctuations and the supply of oxygen and nutrients from the surface water can also play a role. In order to understand the interaction between surface water and groundwater in a highly dynamic RBF system of a large river, bacterial abundance, biomass and carbon production as well as standard chemical parameters were analyzed during a 20 month period under different hydrological conditions. In the investigated RBF system, groundwater table changes exhibited striking dynamics even though flow velocities were rather low under regular discharge conditions. Bacterial abundance, biomass, and bacterial carbon production decreased significantly from the river towards the drinking water abstraction well. The cell size distribution changed from a higher proportion of large cells in the river, towards a higher proportion of small cells in the groundwater. Although biomass and bacterial abundance were correlated to water temperatures and several other chemical parameters in the river, such correlations were not present in the groundwater. In contrast, the dynamics of the bacterial groundwater community was predominantly governed by the hydrogeological dynamics. Especially during flood events, large riverine bacteria infiltrated further into the aquifer compared to average discharge conditions. With such information at hand, drinking water utilities are able to improve their water abstraction strategies and react quicker to changing hydrological conditions in the RBF system.

Updating the Coupling Algorithm between HYDRUS and MODFLOW in the HYDRUS Package for MODFLOW

Core Ideas The coupling algorithm between HYDRUS‐1D and MODFLOW is updated. Pressure head profiles are updated based on the groundwater table and bottom flux after each time step. This eliminates sudden variations in inflow and outflow fluxes with groundwater table changes. The HYDRUS‐based flow package for MODFLOW (the HPM or the HYDRUS package) is an existing unsaturated zone flow package for MODFLOW. In MODFLOW with the HPM, the groundwater modeling domain is discretized into regular grids that can be combined into multiple zones based on similarities in soil hydrology, topographical characteristics, and the depth to the groundwater. Each of these zones is assigned one unsaturated soil profile (the HPM profile). In this model, after every MODFLOW time step, the flux at the bottom of the HPM profile is given as an input recharge flux to MODFLOW. MODFLOW simulates groundwater flow, and the water table depth at the end of the MODFLOW time step is assigned as the bottom boundary condition in the HPM profile. The current coupling algorithm assumes that the groundwater table in the HPM profile remains constant throughout the entire MODFLOW time step. This results in unrealistic sudden inflow and/or outflow fluxes at the bottom of the HPM profile after every time step. The objective of this study was to develop a methodology to eliminate the error in the determination of the recharge flux at the bottom of the HPM profile. This was achieved by updating or modifying the pressure head profile in the HPM profile after every MODFLOW time step. The effectiveness and the applicability of the new coupling algorithm were evaluated using different case studies. The new coupling algorithm is effective in eliminating unrealistic sudden variations in the bottom flux in the HPM profiles.

Charakterystyka hydrologiczna Kosarzewki

<p>W oparciu o materiały hydrograficzne zbierane w Zakładzie Hydrologii od lat 50. XX wieku przedstawiono warunki występowania wód podziemnych i ich rolę w zasilaniu Kosarzewki. Jest to zlewnia o powierzchni 209,3 km<sup>2</sup>, położona 12 km na południe od Lublina, w dorzeczu górnej Bystrzycy. Zasoby wodne tego terenu, ich ilość i jakość, decydują o zaopatrzeniu Lublina w wodę. </p><p>Wody podziemne w zlewni Kosarzewki występują w szczelinowo-porowych, węglanowych skałach górnej kredy oraz paleocenu. O warunkach hydrogeologicznych decyduje tektonika górotworu oraz naprzemianległe występowanie w stropowych partiach skał górnej kredy zróżnicowanych litologicznie warstw decydujących o utrzymywaniu się kilku poziomów wodonośnych Czynniki te zadecydowały o braku ciągłości pierwszego zwierciadła wody, o istnieniu skokowo zmiennych rzędnych zwierciadła wody oraz o istnieniu źródeł w różnym położeniu hipsometrycznym, zarówno w dolinach rzecznych jak też na wysoko wyniesionych równinach denudacyjnych obszaru zlewni.</p><p>Przepływ wód podziemnych następuje z południowego wschodu na północny zachód, zgodnie z układem głównych dolin. W regionalnym drenażu wód podziemnych stwierdza się możliwość podziemnego przepływu wody z lewej części zlewni Kosarzewki do Bystrzycy, która jest głębiej wcięta w podłoże skalne.</p>W strukturze odpływu Kosarzewki dominuje zasilanie podziemne, z którego pochodzi 87% wody rzecznej. Woda podziemna dociera do rzek poprzez bezpośredni drenaż korytowy oraz przez źródła zasilane z głównego poziomu występującego w skałach górnej kredy. W okresie badań stwierdzono synchroniczne zmiany stanów wody podziemnej, wydajności źródeł i przepływu Kosarzewki. Rzeka słabo reaguje na zasilania atmosferyczne, wody opadowe są retencjonowane w podłożu skalnym. Spływ powierzchniowy pojawia się sporadycznie, częściej w okresie przemarznięcia gruntu niż w okresie letnim.

Effects of sea level rise on hydrology: case study in a typical mid-Atlantic coastal watershed

Abstract Sea level rise (SLR) can negatively affect the hydrology of coastal watersheds. However, the relevant information is incomplete and insufficient in existing literature. The objective of this study is to present a modeling approach to predict long-term effects of SLR on changes of flood peak, flood stage, and groundwater table with an assumption that the historical climate would reoccur in the future. The study was conducted for a typical coastal watershed in southeast USA. The results indicate that sea level had been rising at a rate of 4.21 mm yr−1 from 1948 to 1982 but at a faster rate of 5.16 mm yr−1 from 1983 to 2013. At such SLR rates and by 2113, the groundwater table beneath the eastern part of the watershed would be raised by 0.10 to 0.29 m, while the annual mean peak discharge and flood stage at the watershed outlet would be increased by 13.84 m3 s−1 (from 3.63 to 17.47 m3 s−1) and 0.92 m (from zero to 0.92 m), respectively. The other parts of the watershed would be relatively less affected by SLR. For coastal watersheds, SLR will probably raise the groundwater table, and increase the magnitude and occurrence of peak discharge and flood stage.

Use of tree rings as indicator for groundwater level drawdown caused by tunnel excavation in Zhongliang Mountains, Chongqing, Southwest China

Tunnel excavation causes geological, hydrological, environmental and social changes. The effects of groundwater level changes caused by tunnelling on tree growth have been poorly understood. Dendrochronology was used to evaluate the impact of groundwater level drawdown on tree growth. Tree cores of Masson pines were collected from the areas affected by tunnel construction in the Zhongliang Mountains of Chongqing in south-western China to study the effects of tunnel excavation on the growth rate of trees by comparing with tree cores collected from unaffected areas. Excavation and early operation of the first tunnel in the Zhongliang Mountains from 1968 to 1984 caused a groundwater table drawdown in both karst aquifer and non-karst aquifer. The lowered groundwater table significantly reduced the growth rate of pine trees, and the low growth rate remained for 15 years. The effect was experienced up to at least 1 km from the tunnel axis. The decline in tree growth was higher in karst than in non-karst areas, though the effects on the trees of the karst areas were lagging. The high precipitation in 1998 contributed to groundwater recovery, after which the tree growth recovered moderately but not to the original level. Groundwater leakage of the recently excavated tunnels did not affect pine trees heavily, probably because the pines had adapted to the new hydrogeological conditions and new strategies in tunnel inflow management were adopted in the recently excavated tunnels. The use of tree growth rate as an indicator of groundwater table change in tunnelling areas offers a new option to study environmental impacts and the extent of tunnelling effects.

The role of recent tectonics and hydrological processes in the evolution of recurring landslides on the Danube's high bank in Dunaföldvár, Hungary

There are high loess banks prone to landslide along the River Danube in Hungary. One of these is the high loess bank in Dunaföldvár, where several landslides occurred in the last decades. Quantitative relationships between the movements of the high loess bank and the variation of the water level of the River Danube, the ground water table, precipitation and temperature are investigated by two borehole tiltmeters and a vertical borehole extensometer. The twelve-year long observation from 2002 to 2014 made it possible to distinguish between the high bank movements due to slow recent tectonic and geomorphologic processes and the short-period (from hours to months) movements caused by hydrometeorological effects. The results revealed that besides geomorphologic processes recent tectonics can play an important role in the recurrence of landslides in the area. In the investigated period the total tilt of the high bank was 162μrad in the SSE direction according to the geomorphologic and recent tectonic processes in the surroundings of Dunaföldvár. Investigations of the relationships between the high bank movements and the water level of the River Danube, ground water table changes and the precipitation revealed that the tilt magnitudes caused by the ground water table variations are two orders of magnitude greater than the tilts caused by the water level regime of the river and the direct effect of the precipitation on the high bank tilts can be disregarded.

Estimation of Impact of Sea Level Rise on Land and Water Resources When Data Is Sparse - Case of Colombo

This paper highlights investigation and the impacts on the changes in groundwater table caused by sea level rise due to climate change in Wellington New Zealand and translates it to possible impacts in Colombo Sri Lanka. Similarly the possible loss of land due to elevated sea level rise has been investigated. In the past 100 years sea level raised on average by 0.2m in Wellington region and it is predicted that by the 2090 sea level will increase by 0.8 m and by 2115 almost 1m. Therefore an investigation has been carried out by developing a three-dimensional hydrodynamic numerical model. Numerical model was developed using comprehensive groundwater modelling package FEFLOW 6.1. Once the model was developed and calibrated, four scenarios were investigated. Scenario 1 assumed the increase of 0.5 m of the mean seawater level (MSL). Scenario 2, Scenario 3 and Scenario 4 assumed an increase of 1.0 m, 1.5 m and 2.0 m MSL respectively. The changes were compared in nine observation bores and the results are presented. Thereafter taking into consideration the variability of rainfall these estimations have been translated for Colombo. The loss of land is also analysed for those four cases. The loss of the land due to sea level rise was estimated by using ArcGIS (ESRI, 2012). The affected area by the sea level is defined by the corresponding contour, 0.5 m, 1.0 m, 1.5 m and 2.0 m, and the coastline which corresponds to 0 m contour and the sea level at present day. Again these results have been translated to Colombo and presented.

Sezonowa zmienność zasobów wód podziemnych o zwierciadle swobodnym w zlewni Pilicy

<p>The paper attempts to identify seasonal variability of groundwater table in the Pilica catchment. Procedure created by Ch. G. Markham was used. It allows to compare results with analogical characteristics of other aquifers from central Poland. Sixteen piezometers were used for the research.</p><p>They represent shallow aquifers located in the Pilica catchment and its surrounding and they are part of a measurement network of PIG-PIB (years from 2003 till 2014 were used). All of the aquifers with 10 years data series were chosen for the analyzed group. They represent the whole spectrum of occurrence of groundwaters in the Pilica catchment.</p><p>Before the analysis homogeneity of time series was checked by two statistical tests: parametric F-Snedecor test (exams null hypothesis about variance equality) and non-parametric series test (exams null hypothesis about origin of two samples from the same general population). All of numeric strings were statistically homogeneous.</p><p>Time series of mean monthly depth to groundwater table in all piezometers were changed into groundwater ordinates. In that way, maximum values are compared with the maximum level of groundwater table. Next, for all the aquifers the Markham characteristics of seasonal variability were calculated. First of them is seasonality index (IS) and it ranges from 0 to 100%. The second characteristic is time of concentration (WPK). During the interpretation of WPK values it is important to remember that this characteristic shows only time of concentration (it must not be associated with terms of maximum level of the examined phenomenon).</p><p>Aquifers in the Pilica catchment are characterized by differential seasonality index raning from 1 to 30%. It means that rhythm of groundwater table changes is not seasonal in part of aquifers. Despite that, the seasonal variability of groundwater level is stronger in the Pilica catchment than in other aquifers in central Poland (IS is on average almost double). Time of concentration coefficients are differential too. They occur from February to July in the Pilica catchment, while in the whole central Poland they are concentrated in two terms (late winter and summer). Unlike other parts of central Poland, changes of groundwater resources are characterized by poor correlation with hydrogeological parameters of aquifers or mean depth to the groundwater level in piezometers in the Pilica catchment.</p>

Fine-grained detection of land use and water table changes on organic soils over the period 1992⿿2012 using multiple data sources in the Drömling nature park, Germany

The construction of consistent time series of land use presents a key challenge when accounting for elective land use-based activities under the Kyoto Protocol (wetland drainage and rewetting (WDR), cropland management (CM) and grazing land management (GM)), in which current land use-driven greenhouse gas emissions are compared to a reference situation in 1990.This case study is the first to demonstrate the feasibility of using high-resolution land-use proxies from different datasets for Kyoto accounting in a data-rich case study region in Germany. The study region is characterised by organic soils and has been subject to significant nature conservation measures, including land-use changes, reductions in land-use intensity and changes in groundwater table depth.A consistent time series of 20 years of land use with a spatial resolution of 0.01ha was created from various fine-grained spatial datasets for organic soils in the Drömling nature park by applying a newly developed ⿿translation key⿿. The translation key accounted for systematic differences in legends and thematic resolution. We also tested whether the land-use datasets served as trustworthy proxies for groundwater table depth.Land use in the Drömling nature park became less intensive during the study period of 1992⿿2012. The greatest land-use change (142hayear⿿1, 1.14% year⿿1) occurred between 2000 and 2008. This was in line with management measures undertaken in the nature park. The centre of the nature park became wetter and there was an increase in the share of grassland and more natural vegetation types.The groundwater table correlated with land use and land-use intensity on organic soils in the study area throughout the entire period. Land-use changes were accompanied by altered groundwater tables, except for the conversion from cropland to grassland.Our study indicates that detailed land-use time series can serve as a semi-quantitative proxy for groundwater depth, but that any robust quantitative assessment of water table changes requires in situ data, e.g. from a network of dipwells. Therefore, the combination of land-use and dipwell data provided an accurate basis for estimating GHG emission reductions from drained organic soils since 1990, which is the centre of the Kyoto activity WDR, but also part of afforestation/reforestation (AR) and deforestation (D), forest management (FM), CM and GM. Even the detailed land-use time series on its own would fulfil the requirements for WDR accounting, although with considerable uncertainty about the drainage status of the organic soils. We present the study area of organic soils as a showcase for combining the difficult issues of monitoring changes in land-use intensity as well as in soil wetness, the latter being most relevant for organic soils. The methodology is equally applicable to and relevant for mineral soils.

Modeling saline water intrusion in Nagapattinam coastal aquifers, Tamilnadu, India

Unexpected mistreatment of groundwater from coastal aquifers may possibly cause salt water intrusion in coastal aquifers. Coastal areas are mostly overpopulated with productive agricultural lands and expanded irrigated farming actions. Field and modeling studies were started to consider the special effects of possible seawater intrusion into the coastal aquifers. Groundwater levels were measured at 61 locations in Nagapattinam and Karaikal coastal region, identified flow direction pointing toward the coast with no major change in groundwater table. Groundwater samples were collected and analyzed for major ionic parameters, represented higher concentration of conductivity, total dissolved solids, sodium and chloride along the coastal parts of the study area. A computer package for the simulation of dimensional variable density groundwater flow, SEAWAT, has been used to model the seawater intrusion in the coastal aquifers of the study area. The model was stimulated to predict the amount of seawater incursion in the study area for a period of 50 years. The simulation results signify saline water intrusion mainly due to up coning of saline water owing to over drafting of groundwater.

Quantifying the impact of irrigation on groundwater reserve and crop production – A case study in the North China Plain

The North China Plain (NCP) is one of the main grain production regions in China. However, the annual double cropping system of winter wheat and maize consumed a large amount of groundwater, has led to decline in groundwater table. For conservation of groundwater resource, deficit irrigation is promoted to reduce irrigation water use in recent years. This study combined process-based modeling and experimental data together to evaluate the effects of different irrigation strategies on crop production and groundwater table change for the past three decades in NCP. Data from a six year field trial (2006–2012) under four irrigation schedules and 28 year (1984–2012) field experiment under full irrigation was used to test the agricultural production systems simulator (APSIM) to simulate the responses of winter wheat and maize to different irrigation management. The results showed that APSIM model could well simulate the grain yield and water consumption of the double cropping system under the changing climate and management practices. Simulation results with four irrigation scenarios (critical stage irrigation (CI), minimum irrigation (MI), rainfed (RF) and full irrigation (FI)) from 1984 to 2012 showed that irrigation water use efficiency (IWUE) was highest under CI, although changing from FI would lead to reduction in average annual grain yield by 19.5%, 33.7%, and 58.8% under CI, MI and RF, respectively. Even the minimum irrigation strategy (MI—one irrigation for each crop) will result in continuous decline in the groundwater table, implying an inevitable future shift to alternative cropping systems like dryland wheat-maize system, single wheat or maize. Such change will likely result in lower crop productivity and increased inter-annual variability in crop yields, which will demand improved risk management strategies to minimize loss in bad year while maximize return in good years.