Groundwater Level Response Research Articles

Groundwater Allocation Using a Groundwater Level Response Management Method—Gnangara Groundwater System, Western Australia

The Gnangara groundwater system (Gnangara system) is an important source of groundwater for Perth, Western Australia: in the order of 350 GL of groundwater is abstracted annually. The Gnangara system also sustains groundwater dependent ecosystems (GDEs), mostly wetlands and native vegetation. Declining groundwater levels across the system have led to impacts on a number of key GDEs. Western Australia’s Department of Water recently prepared a Water Management Plan for the Gnangara system. Allocation limits were reviewed as part of the plan preparation. To assist in reviewing allocation limits, an adaptive Groundwater Level Response Management (GWLRM) methodology was developed and implemented. This paper describes the methodology and its application to the Gnangara system. The methodology was developed to be used as a corrective tool for the short- and medium-term, to assist in achieving long-term sustainability of groundwater management in the context of changing climate and declining groundwater levels. The GWLRM methodology is based on groundwater storage depletion and can be applied to existing allocation limits as an interim tool to assist in making management decisions aimed at recovering groundwater resources. The key to the GWRLM correction is that it will direct water allocation towards sustainable levels on the basis of measured trends. Allocations corrected through application of the GWRLM would therefore represent interim and improved water allocation figures. GWLRM can also identify potential problem areas where the principles or calculations used for long-term sustainable groundwater allocation would need to be reviewed. For the Gnangara system, the calculated storage changes or GWLRM corrections were considered together with results of predictive modelling as part of an expert panel process to derive a more sustainable interim groundwater allocation regime while further research is being completed.

Effect of the ecological water conveyance project on environment in the Lower Tarim River, Xinjiang, China

The dynamic response of groundwater level is examined in traverse and lengthways directions. Take the Yinsu section for an example, we have simulated groundwater levels before and after water-conveyance every time and calculated the incidence of groundwater on the both sides of the river. It is noted that the effect keeps growing with the water-delivery times increasing, from 570 m after the first times to 3,334 m after the eighth times. In addition, this paper involves the temporal response of the natural vegetation to water conveyance, vegetation coverage, planted-species number, dominant position and species diversity from 2002 to 2006. The findings indicate that the positive influence of ecological water conveyance project (EWCP) on the ecosystem in the Lower Tarim River is a long-term process. In this paper, we try to calculate water required for recovery of damaged ecosystem by using data available. This project is likely the base of research on water demand and the reference of measures for research on ecological water conveyance effect.

The influence of drought and anthropogenic effects on groundwater levels in Orissa, India

Summary Investigating the response of groundwater levels to the extreme weather events provides essential information for sustainable planning and management of water resources. The aim of this study was to identify and quantify the groundwater level trend of the state Orissa (India) to understand the forcing mechanism of droughts in conjunction with the anthropogenic pressure using the non-parametric Mann–Kendall statistical procedure. The pre- and post-monsoon groundwater level records of 1002 monitoring stations during the period 1994–2003 were analyzed. The results show that the drawdowns due to deficient rainfall during dry years, high temperatures, and anthropogenic pressure have not been recovered through the recharge in wet years. However, this study does not determine whether drought, high temperatures or anthropogenic effects have had largest influence on the groundwater levels decline. The cases of significant water table declines are higher in number than those expected to occur by chance. In the pre-monsoon season, 59% of the monitoring stations experienced groundwater declines as against 51% in the post-monsoon season for the study area as a whole. This could be interpreted that the fluctuation is not a part of noise, but that a signal is being identified. Further, the trend result showed wide spatial and seasonal differences. Irrespective of seasons, the consolidated rock formation that covers 80% of the geographical area experienced significant water table decline. However, the semi-consolidated and unconsolidated formations experienced water table decline in the pre-monsoon (summer) season only. The vulnerable sites where the groundwater-level declined significantly were identified so that recharge measures could be taken up.

Estimation of layered aquifer diffusivity and river resistance using flood wave response model

A convolution equation and a discrete ramp kernel equation for the application of the flood wave response were applied to estimate aquifer diffusivity and river resistance using the groundwater levels of a selected well in the Mangyeong-river floodplain. The aquifer diffusivity and river resistance are the key parameters to explain the hydraulic connection between aquifer and river. Groundwater level during a zero rainfall period was used so that the effect of rainfall recharge on groundwater level could be neglected. Selecting an appropriate flood wave and undertaking correction of the preceding recession or trend of the groundwater level and the river stage had to be performed prior to hydrograph matching. The observed and calculated groundwater level responses generated by a flood wave response model to the river stage were matched to each other, and an optimal value of the aquifer diffusivity and river resistance were obtained. The proposed method is an effective and economical means to estimate aquifer diffusivity and river resistance to characterize the hydraulic interaction between groundwater and river.

Analysis of water-level response to rainfall and implications for recharge pathways in the Chalk aquifer, SE England

Summary Water table response to rainfall was investigated at six sites in the Upper, Middle and Lower Chalk of southern England. Daily time series of rainfall and borehole water level were cross-correlated to investigate seasonal variations in groundwater-level response times, based on periods of 3-month duration. The time lags (in days) yielding significant correlations were compared with the average unsaturated zone thickness during each 3-month period. In general, for cases when the unsaturated zone was greater than 18 m thick, the time lag for a significant water-level response increased rapidly once the depth to the water table exceeded a critical value, which varied from site to site. For shallower water tables, a linear relationship between the depth to the water table and the water-level response time was evident. The observed variations in response time can only be partially accounted for using a diffusive model for propagation through the unsaturated matrix, suggesting that some fissure flow was occurring. The majority of rapid responses were observed during the winter/spring recharge period, when the unsaturated zone is thinnest and the unsaturated zone moisture content is highest, and were more likely to occur when the rainfall intensity exceeded 5 mm/day. At some sites, a very rapid response within 24 h of rainfall was observed in addition to the longer term responses even when the unsaturated zone was up to 64 m thick. This response was generally associated with the autumn period. The results of the cross-correlation analysis provide statistical support for the presence of fissure flow and for the contribution of multiple pathways through the unsaturated zone to groundwater recharge.

Temporal and spatial variability response of groundwater level to land use/land cover change in oases of arid areas

This paper conducts a case study on the impacts of land use/cover change (LUCC) on the temporal and spatial variability of the groundwater level in an arid oasis in the Sangong River Watershed by using the geographical information system (GIS), remote sensing (RS) and geostatistical methods. The temporal and spatial variability of the groundwater level in the watershed in 1978, 1987 and 1998 is regressed by using the semivariogram model and Kriging interpolation. The LUCC classification maps derived from the aerial images in 1978, Landsat TM image in 1987 and Landsat ETM image in 1998 are used to superpose and analyze the conversion relationship of LUCC types in the regions with different isograms of the groundwater depth. The results show that the change of groundwater recharge was not so significant in the whole oasis, but the temporal and spatial LUCC was significant either in the normal flow periods or in the high flow periods during the 20-year period from 1978 to 1998, and there was a close correlation between them. There is generally a moderate spatial correlation of groundwater level (33.4%), and the spatial autocorrelation distance is 17.78 km. The regions where the groundwater level is sharply changed are also the regions where the land resources are increasingly exploited, which include mainly the exploitation of farmlands, woodlands, and building, industrial and mining lands. The study reveals that the LUCC affects strongly the temporal and spatial variability of the groundwater level in the arid oasis. The study results are of direct and practical significance for rationally utilizing shallow groundwater resources and maintaining the stability of the arid oasis.

地震に関連した地下水の応答：2004年釧路沖の地震（M7.1）における地下水位の変化

地震に関連した地下水の応答：2004年釧路沖の地震（M7.1）における地下水位の変化

GROUND WATER/SURFACE WATER RESPONSES TO GLOBAL CLIMATE SIMULATIONS, SANTA CLARA-CALLEGUAS BASIN, VENTURA, CALIFORNIA

ABSTRACT: Climate variations can play an important, if not always crucial, role in successful conjunctive management of ground water and surface water resources. This will require accurate accounting of the links between variations in climate, recharge, and withdrawal from the resource systems, accurate projection or predictions of the climate variations, and accurate simulation of the responses of the resource systems. To assess linkages and predictability of climate influences on conjunctive management, global climate model (GCM) simulated precipitation rates were used to estimate inflows and outflows from a regional ground water model (RGWM) of the coastal aquifers of the Santa Clara-Calleguas Basin at Ventura, California, for 1950 to 1993. Interannual to interdecadal time scales of the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate variations are imparted to simulated precipitation variations in the Southern California area and are realistically imparted to the simulated ground water level variations through the climate-driven recharge (and discharge) variations. For example, the simulated average ground water level response at a key observation well in the basin to ENSO variations of tropical Pacific sea surface temperatures is 1.2 m/°C, compared to 0.9 m/°C in observations. This close agreement shows that the GCM-RGWM combination can translate global scale climate variations into realistic local ground water responses. Probability distributions of simulated ground water level excursions above a local water level threshold for potential seawater intrusion compare well to the corresponding distributions from observations and historical RGWM simulations, demonstrating the combination's potential usefulness for water management and planning. Thus the GCM-RGWM combination could be used for planning purposes and — when the GCM forecast skills are adequate — for near term predictions.

Evaluation and rehabilitation of dam seepage problems. A case study: Kafrein dam

The intention of this study is to locate the probable sources of the Kafrein dam seepage problem. A methodology known as excitation-response analysis will be considered. Analytical expressions, depicting the groundwater level response in the underlying aquifer as a result of changes in the reservoir water level, were derived from a linearized groundwater flow equation for one-dimensional semi-infinite, isotropic and homogeneous porous media. The results revealed that a large proportion of the seepage water originates from a site at a distance about 1 km from the observation point M1 and streamlines along the existing faults. Emphasis in this work was also placed on controling and mitigating the seepage problem.

A model for predicting groundwater level response to meteorological changes

Abstract A simple model, based on the overall soil water balance, has been developed for the prediction of groundwater levels in response to meteorological changes. The model consists of two parts as follows: A soil moisture deficit model which uses daily rainfall and potential evapo-transpiration data to estimate the effective rainfall entering the ground beyond the influence of evapo-transpiration. A model relating the effective rainfall to the water table and predicting the groundwater level response. Rainfall, potential evaporation and water level records are required for at least two years in order to perform a split record test. The data from the first year are used for calibrating and from the second year for testing the model. The model has been applied to a cliff top site adjacent to the degrading coastal cliffs at Naish Farm, near Highcliffe, Hampshire. The necessary data has been collected over the two year period from October 1982 to October 1984. The groundwater level data used is for the upper permeable layer of Plateau Gravel. The Plateau Gravel acts as a groundwater store, supplying seepage both down into the underlying Barton Clay and, under winter conditions, outwards to the cliff face. The meteorological data were obtained by setting up a local weather station. The results show a good model fit to the observed data. The model is suitable for general application. It is considered that it may prove of particular value for areas with active landslides as a means of understanding the incidence and rates of slope movements.

Response of groundwater levels to rainfall and to leaf growth of farm plantations near salt seeps

Clearing of native forest has caused a rise in soil water tables and secondary salinisation in south Western Australia. An experiment in reclamation began in May 1976 with the replanting of tree vegetation near salt seeps. Spectral analysis was used to relate the subsequent changes in static water levels of the groundwater to rainfall input and progressive leaf area index of two plantations on a single subcatchment. The upslope static water levels lagged the seasonal rainfall by 3–4 months, whereas the midslope levels lagged rainfall by ∼ 1 month. Increasing leaf area of the plantations corresponded to decreasing groundwater levels in their vicinity.

Determination of Bulk Rock Properties From Ground-water Level Fluctuations

The response of ground-water levels to tides and changes in barometric pressure provides an in-situ measure of the response of the rock-water system to changes in stress. Tidal and barometric efficiencies can thus be expressed in terms of drained and undrained moduli. In addition, if the various moduli are known from laboratory measurements, the laboratory equivalents of both tidal and barometric efficiency can provide an estimate of the specific storage. The method is demonstrated to provide reasonable and consistent results when applied to various rock types of differing rigidity.