Height Of Groundwater Table Research Articles

Rainfall Versus Water Balance Components Using R Software: A Case Study on a Micro-watershed in the Mid-lands of Kerala

Quantitative information on an area’s water balance components is essential to plan water management activities. In most cases, these water balance components, viz. rainfall, runoff, soil moisture, groundwater storage, and evapotranspiration, will be missing, especially in the developing world. At the same time, most countries have rainfall data in a reasonably acceptable spatial resolution. Hence, if a relationship between rainfall and other water balance components can be developed, then using these relations, the values of those water balance components can be determined. Hence, a study has been taken up in which important water balance components, viz. rainfall, runoff, soil moisture, the height of groundwater table from MSL, and evapotranspiration, are measured from a watershed, and the relationship between rainfall and other components have been determined through regression analysis. R software was used to determine relationships between rainfall and other water balance components. The Pearson’s correlation coefficient (r) between rainfall vs. runoff was 0.83, rainfall vs. soil moisture was 0.80, rainfall vs. the height of GW table from MSL was 0.72, and rainfall vs. evapotranspiration was -0.64, which indicates a good correlation in the majority of the cases. The relationship between rainfall vs. runoff, rainfall vs. soil moisture, rainfall vs. the height of the GW table, and rainfall vs. evapotranspiration was a polynomial equation with degrees 4, 3, 5, and 3, respectively. The study concludes that it is possible to estimate most other water balance components using the regression estimates by measuring the rainfall. These relationships can be used effectively in water management programs.

Design of open drains by solving Richards equation and artificial neural networks

The perfect design of open drains requires understanding the effect of the different design parameters on groundwater table. The paper objective is to perform sensitivity analysis to show the effect of the drainage flow rate, the distance between the bed of the open drain and the bottom impervious layer, the drain bed width, the spacing between drains, and the soil type (design parameters) on the maximum height of groundwater table above the open drain bed. HYDRUS software, Dupuit equation, and artificial neural networks (ANNs) are used. Comparison is performed between HYDRUS and Dupuit equation for simulating water flow in unconfined aquifer between two water ways. The predicted groundwater table using HYDRUS is above the other one from Dupuit equation. ANNs were used to predict the maximum height of groundwater table from its design parameters. MATLAB code is written to simply use the previous ANNs to find the best drain design.

Stability of complex rock tunnel face under seepage flow conditions using a novel equivalent analytical model

The longitudinally inclined layered rock masses under seepage flow conditions have an important impact on tunnel face stability. To solve this issue, a novel equivalent analytical model is proposed in this paper. This model settles the puzzle that the traditional model of limit analysis cannot directly determine the hydraulic head by treating the distribution hydraulic head at the anterior aspect of the tunnel face with the equivalent method, that is, without the tedious calculation by the numerical software. The seepage force is directly considered as a body force in this analytical model. Then, combined with the mirror-image method, layered discretization technique, limit analysis method, and Hoek-Brown yield criterion, an analytical expression for stability determination can be derived. The main factors affecting the stability of tunnel face are analyzed, such as the inclination angle of the flow line, the inclination angle of the rock layer, hydraulic conductivity, rock quality, excavation disturbed zone (EDZ), and the groundwater table height. The calculated diagrams have a certain guiding effects for tunnel construction.

Model predictive controlled subsurface drainage and irrigation for peatland groundwater management

A dynamic simulation model for the water balance in a field with controlled subsurface drainage and irrigation is derived. The model is then applied to groundwater table height control, using the model predictive control (MPC) paradigm. The nonlinear constrained MPC problem is solved and results illustrated in simulations. The role of automation of controlled subsurface drainage in cultivated peatlands is discussed.

Stability of rectangular tunnel in Hoek–Brown rocks under steady-state groundwater flow

This research study aims to determine the stability of a rectangular tunnel excavated in rock masses obeying Hoek–Brown yield criteria under steady-state groundwater flow using lower bound limit analysis. During tunnelling in the presence of groundwater table (GWT) seepage forces are generated, which causes a decrease in the stability of rock mass. The total head distribution due to seepage is obtained by using two-dimensional finite element software Optum G2. The stability has been presented by a non-dimensional number σci/γ′maxH obtained for various combinations of B/h, H/h, Hw/h, σci/γwh, mi, GSI and D where B and h are width and height of the tunnel, respectively, H is the depth of the tunnel from the ground surface and Hw is the height of GWT from the tunnel roof, respectively, σci and γ′ are uniaxial compressive strength and submerged unit weight of rock, respectively, γw is the unit weight of water and mi, GSI and D are the Hoek–Brown parameters.

A modified SWAT module for estimating groundwater table at Lethbridge and Barons, Alberta, Canada

Groundwater is a priceless resource in Alberta and therefore, estimating groundwater are crucial to identifying and promoting holistic and integrated management of groundwater-surface water. However, it is a challenge to simulate groundwater storage due to the current rudimentary representation of two-way groundwater-surface water exchange in current hydrologic models, such as Soil and Water Assessment Tool (SWAT), which, in turn, limits our ability to predict land-atmosphere processes and groundwater storage. In this study, we modified the SWAT model to improve module of evapotranspiration in two-way groundwater-surface water exchange. The modified SWAT was calibrated and validated against the groundwater table height and evapotranspiration from 2008 to 2011 period at two location (Lethbridge and Barons) Alberta, Canada. The results showed that the modified SWAT model predicts the groundwater table height very well at both locations. The modified model predicted the daily groundwater table height with R2 values of 0.86 and 0.89 in the calibration period (2008–2009), 0.81 and 0.83 for the validation period (2010–2011) at Lethbridge and Barons, respectively. The Nash-Sutcliffe model efficiency (NSE) for daily groundwater table height was 0.69 and 0.71 during calibration periods (2008–2009) while the model gives lower values of NSE 0.65 and 0.67 for validation periods (2010–2011) at Lethbridge and Barons, respectively. Similarly, the model estimates evapotranspiration well with correlation coefficient (R2) of 0.77 during the calibration period and 0.81 for validation period. Our result showed that the modified SWAT model did improve estimates to dynamic groundwater table heights.

Landslide Susceptibility Analysis (LSA) using Deterministic Model (Infinite Slope) (DESSISM) in the Kota Kinabalu Area, Sabah, Malaysia

A practical application for landslide susceptibility analysis (LSA) based on two dimensional deterministic slope stability (infinite slope model) (DESSISM) was used to calculate factor of safety (FOS) and failure probabilities for the area of Kota Kinabalu, Sabah. LSA is defined as quantitative or qualitative assessment of the classification, volume (or area) and spatial distribution of landslides which exist or potentially may occur in an area. In this paper, LSA value can be expressed by a FOS, which is the ratio between the forces that make the slope fail and those that prevent the slope from failing. An geotechnical engineering properties data base has been developed on the basis of a series of parameter maps such as effective cohesion (C’), unit weight of soil ,)?(depth of failure surface (Z), height of ground water table (Zw), Zw/Z dimensionless (m), unit weight of water ,)w?(slope surface inclination (s) and effective angle of shearing resistance (?). Taking into consideration the cause of the landslide, identified as groundwater change, the maximum groundwater level recorded corresponding to the actual situation of the most recent landslide is considered in this study. The highest probability value of the various scenarios was selected for each pixel and final LSA map were constructed. It has been found from this study that s and Zw parameters have the higher influence on landslide instability. The result validation between the examined LSA map and result of landslide distribution map (LDM) were evaluated. This DESSISM had higher prediction accuracy. The prediction accuracy is 84%. The resulting LSA maps can be used by local administration or developers to locate areas prone to landslide area, determine the land use suitability area and to organize more detailed analysis in the identified “hot spot” areas.

Effects of vadose zone on groundwater table fluctuations in unconfined aquifers

Above a shallow unconfined aquifer, a considerable amount of water is stored in the vadose zone. Through water exchange with the underlying unconfined aquifer, the vadose zone affects the groundwater table dynamics and overall behavior of the aquifer. In this paper, we examine tide-induced groundwater table fluctuations in unconfined aquifers influenced by vadose zone of finite thickness. Under the condition of small aquifer thickness (D) compared with the groundwater wavelength (L) (i.e., μ2=D/L2≪1) and small boundary oscillation amplitude (a) (i.e., ε=a/D≪1) (where μ2 and ε are two parameters), an approximate analytical solution was derived to quantify systematically the vadose zone effects, with a particular consideration of capping by the ground surface, i.e., the upper boundary of the vadose zone. Depending on the extent to which the capillary rise is truncated by the ground surface, the vadose zone enhances the groundwater table fluctuations in an unconfined aquifer. However, the mean groundwater table height and exchange between surface water and groundwater are reduced due to the presence of the vadose zone. These effects are intensified with increased capillary rise, but weakened as the vadose zone thickens. This study provides a criterion for assessing the importance of vadose zone in modulating the response of unconfined aquifers to low-frequency forcing oscillations such as tides.

Examining the uneven growth rates of rubber trees: the case study at a plantation in North-Eastern Thailand

This study seeks to empirically identify significant factors that contribute to the uneven growth rates of rubber trees using statistical analysis of collected data. The uneven growth rate of rubber trees has caused to the variation in maturity of rubber trees which may then affect the economic returns of the rubber estate. The revealing of the factors may help to reduce the uneven growth rate and the losses caused by this problem. Applying the Tobit model analysis, the results reveal that the land slope and forest boundaries are significant primary factors in influencing the growth rate of rubber trees. Exhibiting the results in three dimensional plots shows that topsoil erosion leads to soil accumulation at foothills of land slopes and this can inhibit growth. On the other hand, ground water table height does not affect the growth rate significantly.

Assessment of the Nexus between Groundwater Extraction and Greenhouse Gas Emissions Employing Aquifer Modelling

One of the main sources of Greenhouse Gas Emissions (GHG) is electricity consumption which is getting used for different purposes.Water pumping, especially, pumping from deep groundwater resources consumes a lot of energy. In arid and semi-arid areas, in which groundwater is the only source of water, water pumping is done for different purposes such as agricultural, industrial and urban uses. Kerman plain is one of these arid and semi-arid areas which is located in South East of Iran. Groundwater reliance and aquifer decline are the most prominent challenges that this area is faced with in recent years. This challenges increase the demand for more electricity consumption to pump water from the aquifer so that CO2 emissions will be increased. A large percentage of water extraction from the aquifer is used for agricultural purposes. In this paper, by modelling Kerman plain aquifer with MODFLOW software by using Geographical Information System (GIS) database and also studying height of groundwater table from 1999 to 2012, electricity energy consumption of groundwater extraction for agricultural, industrial and urban water supply is calculated and the CO2 emissions trends resulted from electricity energy consumption is evaluated. Then model results are examined for a business as usual (BAU) scenario of changes in water resources. As a result the amount of CO2 emitted from groundwater abstraction by three mentioned sectors is calculated for specified time horizon. Finally, some suggestions are presented for reducing greenhouse gas emissions for the time horizon.

Intergration of GIS Using GEOSTAtistical INterpolation Techniques (Kriging) (GEOSTAINT-K) in Deterministic Models for Landslide Susceptibility Analysis (LSA) at Kota Kinabalu, Sabah, Malaysia

A practical application for landslide susceptibility analysis (LSA) based on GEOSTAtistical INterpolation Techniques (Kriging) (GEOSTAINT-K) for a deterministic model was used to calculate the factor of safety (FOS) and failure probabilities for the area of Kota Kinabalu, Sabah. In this paper, the LSA value can be expressed by a FOS value, which is the ratio of forces that make the slope fail and those that prevent the slope from failing. A geotechnical engineering properties data base has been developed on the basis of a series of parameter maps such as effective cohesion (C’), unit weight of soil (g), depth of failure surface (Z), height of ground water table (Zw), Zw/Z dimensionless (m), unit weight of water (gw), slope surface inclination (?) and effective angle of shearing resistance (f). Taking into consideration the cause of the landslide, identified as groundwater change, two scenarios of landslide activity were studied. Scenario 1 considered the minimum groundwater level recorded corresponding to the actual situation of the most recent landslide while Scenario 2 considered the reverse. A simple method (infinite slope model) for error propagation was used to calculate the variance of the FOS and the probability that will be less than 1 for each pixel. The highest probability value of the various scenarios was selected for each pixel and final LSA 1 (scenario 1) and LSA 2 (scenario 2) maps were constructed. The validation between the examined LSA 1 and LSA 2 maps and the results of the landslide distribution map (LDM) were evaluated. This deterministic model had higher prediction accuracy. The prediction accuracy was 81 % and 85 %, respectively. In general for both factors, the LSA 2 map showed higher accuracy compared to the LSA 1 map. The resulting LSA map can be used by local administrators or developers to locate areas prone to landslides, determine the land use suitability and organize more detailed analysis of the “hot spot” areas identified.

Experimental investigation of effect of tide on coastal groundwater table

In this article, a tide simulation system based on a two-way water pump technique is developed. Using this system and numerical simulations, the groundwater table fluctuation characteristics, relative over height of groundwater table, and influencing factors of over height are investigated. The experimental and numerical results indicate that the groundwater table fluctuation is of periodic, and of asymmetric. The amplitude of groundwater table fluctuations decreases with the increase of the onshore distances. There are phase lags of groundwater table fluctuations for different monitoring points. The tide can bring about remarkable over height of coastal groundwater table. The dominating factors bring about over height include the tide amplitude, aquifer thickness and tide frequency. Under experimental conditions, the relative tide amplitude over height may exceeded 50% of the maximal tide amplitude, and reach about 10% of aquifer thickness.

Linking vegetation pattern to hydrology and hydrochemistry in a montane river floodplain, the Šumava National Park, Central Europe

Cover of higher plants (in 4 × 4 m plots), groundwater table height, and water chemistry in boreholes were sampled at 43 sites along three cross-sectional transects in a flat floodplain of the Upper Vltava River in the Sumava Mountains (Sumava National Park, Czech Republic). The goal was to describe the relationships between vegetation and alluvial environment. Correlations between hydrochemical and plant community characteristics were calculated, and Canonical Correspondence Analysis (CCA) was used to express relationships between the abiotic factors and vegetation. The following characteristics were significantly correlated with the vegetation pattern: mean height of the water table, distance from the river, pH, and concentration of NH4 and humic acids in the groundwater. Two distinct zones were distinguished in the floodplain: Zone I was under direct influence of the river, and exhibited higher pH and ammonium content in a fluctuating groundwater table. Zone II, covering more than half of the floodplain extent, was under the prevailing influence of water coming from the adjacent upland, and exhibited lower pH, higher content of humic acids, and a higher and relatively stable groundwater table. A diverse mosaic of the riparian communities, especially of tall-sedge and tall-grass marshes and alluvial meadows, was typical for the former zone, while peatland vegetation characterised the latter one. The floodplain exhibited a rather oligo- to mesotrophic status with only very local eutrophication, and harboured diverse and valuable plant communities. The protection of this floodplain should be among the priorities of the National Park authorities.

Nitrate Dynamics in Shallow Groundwater and the Potential for Transport to Off-Site Water Bodies

Large quantities of the nitrate leaching below the crop root-zone, particularly during the wet season, in the tropical Far North Queensland (FNQ) of Australia, may be entering off and on-site the water bodies. The objectives of this study were to (i) provide quantitative information on NO3-N in the shallow fluctuating groundwater (GW) that develops during the rainy season (January through May) in the Johnstone River Catchment (JRC) of FNQ and (ii) determine whether this NO3-N is potentially transportable to creeks/streams. The NO3-N concentration and GW table heights were monitored, at least at weekly intervals, in 6 piezometers, installed to 8.5–12.0 m depth in 6 different soil types under fertilized sugarcane (Saccharum Officinarum-S) in the JRC during the 1999 rainy season.Depending on the location of piezometers on the landscape and time of water sampling, the GW table fluctuated between from 1.5 to 11.5 m abovethe piezometer bottom. The NO3-N concentration in the fluctuating GW also showed spatio-temporal dynamics and it ranged from 0.60 to 3.70 mg L-1. The NO3-N adsorbed at anion exchanges sites, up to 10 m depth, ranged from 154 to 3956 kg ha-1, compared with 21 kgha-1 under rainforest. In the fluctuating GW, the NO3-N concentration increased with increasing GW table height and the NO3-N adsorbed at anion exchange sites (R2 = 0.96). The NO3-N load in the GW ranged from 40 to 110 kg ha-1 and it increased with increasing GW table and GW NO3-N concentration. The estimated N-load in the GW that was discharged into creeks/streams when the GW receded ranged from 21 to 81 kg ha-1. The results provide evidence that a(i) a major proportion of the NO3-N that was leaching below the sugarcane root-zone entered the shallow GW that developed during the rainy season, and (ii) a significant proportion of the NO3-N inthe GW was transported to creeks/streams when the GW table receded.

Analytical Solution for Transient Water Table Heights and Outflows from Inclined Ditch-Drained Terrains

This paper presents two analytical solutions of the linearized Boussinesq equation for an inclined aquifer, drained by ditches, subjected to a constant recharge rate. These solutions are based on different initial conditions. First, the transient solution is obtained for an initially fully saturated aquifer. Then, an analytical expression is derived for the steady state solution by allowing time to approach infinity. As this solution represents the groundwater table shape more realistically, this water table profile is used as an initial condition in the derivation of the second analytical solution for the groundwater table height, and the in- and outflow into the ditches. The solutions allow the calculation of the transient behavior of the groundwater table, and its ouflow, due to changing percolation rates or water level heights in both ditches.

Use of Digitalized Hydrogeological Maps for Evaluation of Salt-Affected Soils of Large Areas

Soil salinity and sodicity is often related to the presence of shallow groundwater. We evaluated the importance of factors that affect soil salinity and sodicity in one typical salt-affected area, the Carpathian Basin. Five hydrogeological maps were used to demonstrate the occurrence of salt-affected soils in the Great Hungarian Plain. The 1:500,000 scale maps showed the depth to groundwater, the concentration of soluble salts in the groundwater, the height of groundwater table above sea level, textural classes of near-surface formations, and the dominant ions in the groundwater. After digitizing the maps, a database was created, and the association between variables was quantified by the uncertainty coefficient. The largest statistical association with the occurrence of salt-affected soils was found for the height of groundwater above sea level, the dominant ions of groundwater, and the textural class of subsurface layers. The hydrogeological maps showed close interrelationships of these factors, therefore no single factor, but a combination of factors, were responsible for the occurrence of salt-affected soil types. Regarding the most frequent categories of hydrogeological variables in which the salt-affected soils occurred, two groups were distinguished: the noncalcareous solonetzes and related soils (26.7% of the Plain) were most frequently associated with clay and the groundwater is dominated by Na + and HCO 3 - with a height above sea level at 80-90 m. The sodic solonchak and calcareous meadow solonetzes cover only 1.5% of the Plain, and these are most frequently associated with sand, where Ca 2+ and HCO 3 - was dominant in the groundwater. However this group did not adhere to one specific zone of groundwater level, and also showed territorial segregation.

A PREDICTION METHOD ON DISPLACEMENT OF FRACTURED ZONE LANDSLIDE

Behaviour of fractured zone landslide is analysed based on the soil mechanics from a stand point of effective stress. Analysis of displacement of landslide is conducted considering the creep phenomenon of clay and the stress level at slip layer. Creep characteristic of landslide clay is investigated by the triaxial creep test. Stress level is obtained by the stability analysis considering strength parameters of clay obtained from slip surface. Relative rate of creep deformation at each stress level corresponding to each height of ground water table is calculated using the results of creep tests. The results of calculation explain qualitatively the behaviour of Nuts and Inuyose landslides.