From the above review of literature, it is clear that urbanization and subsequent changes in land use and land cover has severe adverse implications for the local ecology ( Fig. 1 ). However, the existing studies have, in general, focused on examining bivariate relationships between urbanization and LULC changes ( Alqurashi & Kumar, 2017; Sajjad & Iqbal, 2012 ), urbanization and changes in temperature ( Chapman, Watson, Salazar, Thatcher, & McAlpine, 2017; Wang, Yan, Li, Liu, & Wang, 2013 ), urbanization and changes in rainfall ( Chen, Li, Du, Mao, & Zhang, 2015; Kug & Ahn, 2013 ), or urbanization and changes in groundwaterlevel ( Khazaei, Mackay, & Warner, 2004; Wakode, Baier, Jha, & Azzam, 2018 ). Hence, multivariate relationships amongst urbanization, LULC changes, changes in temperature, rainfall, groundwaterlevel have remained largely unexplored in the literature. The present paper is an attempt to ﬁll in this gap. In other words, the present paper is to examine urbanization and temperature, rainfall and groundwater controlling for their interdependence.
Groundwaterlevel information which is assimilated in the form of soil moisture data works well in most scenarios but there are some exceptions when the simulated water tables from all or most realizations are above the reference water table. Increasing the ensemble size could solve this specific problem, but it is unclear whether this would work in all scenarios. For example, in real-world cases with bias where the simulated water table depths are systematically closer to the surface than the observed water table depth, correction is difficult. In addition, a larger ensemble size also implies of course increased computational costs. From section 4.4.1 we find that the methodology Mix, which updates model states in terms of pressure for the saturated zone and in terms of soil moisture for the unsaturated zone, outperforms the other methods and results in a very good root zone soil moisture characterization. This might be related to the simple setting in our experiments where only the saturated hydraulic conductivity ks is perturbed. The van Genuchten parameters (α and n) and porosity which link the pressure head and soil moisture in the unsaturated zone are constant. While this setting is relatively simple, the focus is on developing assimilation methodologies with TerrSysMP to improve the estimation of root zone soil moisture by assimilating groundwater levels. Additional experiments (section 4.4.2) where α and n are also perturbed together with ks further verified the feasibility of the methodology Mix. There will be additional challenges for the application of the methodology in real-world situations. The van Genuchten model is used to transform the soil moisture to pressure head in the unsaturated zone after EnKF. In real world cases, the relation between soil moisture and pressure head might even not be described correctly by the van Genuchten model. In addition, if the updated soil moisture state is ≥ porosity (from unsaturated to saturated conditions), no back transform is made. For this grid cell, the model predicted pressure head value prior to assimilation is used. In this case, strange pressure profiles might be generated as the states of the surrounding grid cells were either directly updated in terms of pressure (saturated zone) or pressure was indirectly updated via soil moisture (unsaturated zone). It is expected that in the model simulation for the next time step the pressure profile is partly smoothed again.
For reconstruction of the groundwater levels, firstly, comparison was made using a set of statistical criteria, namely R 2 and NS (Table 3.3), calculated between the observed and reconstructed groundwater levels; secondly, these results were further supported by graphical comparison (see Figures 3.9–3.11).Concerning the graphical illustration, to clearly see where the missing values exist over the time series, the original/incomplete groundwater-level time series of each piezometric station is displayed in Figure 3.9. Based on the complete reconstruction of groundwater levels and missing values imputed for all of the piezometric stations, overall, both SSA and MSSA could quite sufficiently reproduce the groundwater levels; the obtained R 2 and NS values tend towards 1 in nearly all the piezometric stations. In companion, MSSA outperformed SSA in terms of complete reconstruction of the groundwater levels, except for P13 and P36 where SSA could return a slightly better performance than MSSA (see Table 3 and Figures 3.10–3.11). Specifically, SSA delivered the best performance in P38 – the calculated R 2 and NS are 0.99 and 0.99, respectively – while we found a poor performance, delivered by SSA, in P15 with R 2 and NS of 0.75 and 0.74, respectively. The same is not true for MSSA, as the best and worst matches between the observed and reconstructed groundwater levels are seen for P51 and P13, respectively. The R 2 and NS calculated for P51 are 0.99 and 0.99, whereas these metrics computed for P13 are 0.81 and 0.81, respectively. Since MSSA is not only reliant upon temporal correlations but also takes spatial correlations into account, in evaluation of this method over SSA in each piezometer, this should be considered (Kondrashov & Ghil, 2006; Kondrashov et al., 2010). Therefore, it can be inferred from the matrix correlation (Figure 3.3a) that there is no strong
The main objective of the paper is to inform about the results of proposal, design, realisation and optimisation of the groundwater extraction system to control ex- cessive rise of groundwater table. The system was used for Nitra Industrial Park, where the Land Rover Jaguar Company is nowadays already completed at north- ern part of the town Nitra in Slovak Republic. For proper construction and opera- tion of the industrial park there was proposed groundwater extraction well system from which the optimum pumping rate should keep the groundwaterlevel at re- quired elevation without causing any depletion to water resources in the adjacent area. To address this challenge a numerical groundwater modelling system using TRIWACO simulation package was applied. Based on available hydrological, ge- ological and hydrogeological data numerous simulations were carried out for steady as well as for transient flow conditions. Furthermore, the system was opti- mised in situ for proper operation of the system and for minimisation of operation costs.
Groundwater flow (discharge) and extractions are the primary factors affecting aquifer storage. The Polda and Bramfield (in a limited way) Lenses have been developed for reticulated public water supply. The Polda Lens has experienced water level decline due to previous over extraction practices. Recent research has refined the understanding of the hydrological processes that operate within these aquifers and has determined the amount of water that is available for extraction with acceptable impacts to the resources. Kappawanta, Talia and Sheringa Lenses have generally only been developed for stock and domestic purposes, and yet the groundwaterlevel trends of these have also notably declined since 1993 (Figs 12, 13). This highlights how dominating effective rainfall is for recharge for both developed and undeveloped lenses.
Spatial coherences of the groundwater situation are usually visualised by professional evaluated maps. Therefore consultant engineers are being authorised by the water supply companies to collect the relevant data from the concerned area and the specific date and start their evaluation with specific software programs. The water supply companies use these evaluated maps to optimise their internal optimisation of water extraction and infiltration to guarantee a continuous groundwaterlevel. For the governmental agencies these maps are essential to observe and to control the regulation properties of all involved water supply companies of a catchment area and to define their legal obligations.
The solution could be compared with the one of Van de Giesen’s et al. (1994), which takes into account the Laplace solution in the case of a forced unsteady drained problem. With no loosing of generality, for the discussion of the solution, the phase 𝜙𝜙 is posed as zero. The Eq. (13) maintains the oscillatory behavior in space and time, since the external forcing is still a sine function, but with respect to the solution in Eq. (4), this one presents a decay in time and also a superposition of modes that assures the decay in space. The transient phase is represented by the exponential time-dependent component, its effects concerns only the first instants of the phenomenon. The last term f(x,t) is instead the one given by the nonhomogeneous solution, dependent on the forcing period. Eq. (13) is a finite function series, unconverging at infinite. However, the solution of Eq. (13) can be evaluated by considering a limited number of modes in Eq. (14) and Eq. (15). For given time, the firsts two terms of Eq. (13) connect the boundaries linearly. The groundwaterlevel oscillation given by these two terms varies in according to the forcing period. The last two terms depend on several factors, i.e. the parameters that characterize the aquifer β and hence the eigenvalues λ 𝑛𝑛 . The function g(x,t) is weakly dependent on the period of the forcing wave; it strongly depends, apart from the modes, on the length of the domain L, on time t and β. The overall descending behavior is led by the parameter λ 𝑛𝑛 : it can be stated that, since it depends inversely on L, the more the domain is wide the more the delay in time is needed to flatten to zero the function g(x,t), once the parameter 𝛽𝛽 is selected. In Fig. 4 the behavior of
Since the area of study located in a semi-arid zone, recharge from rainfall in the area of study is the main source of groundwater recharge. There are many methods for estima- tion of groundwater recharge from rainfall. However, these methods have shown different limitations and they are associated with specific areas, and under specific conditions. There is a direct relation between the fluctuation of the groundwaterlevel and the rainfall. Many studies have been implemented to estimate the groundwater recharge in the area based on different techniques. Melloul and Bachmat (M ELLOUL & B ACHMAT , 1975) have estimated the rainfall in the Gaza Strip based on soil type and rainfall amount. On the other hand IWACO and WRAP (IWACO & WRAP, 1995) have used the chloride mass balance in the area for estimation of recharge. However, each method yields a dif- ferent output as shown in table 4.6 in chapter 4. In this study, two different new methods have been used: Cumulative Rainfall Departure CRD, and Extended model for Aquifer Recharge and soil moisture Transport through the unsaturated Hardrock (EARTH). The results of these two methods were compared with the results obtained by other methods.
There is evidence that the Fractured Rock Aquifer on the eastern side of the fault north of Willunga is stressed. This is an area of intense groundwater extraction for irrigation. The decline became evident due to sudden a decrease in water supply to a nearby spring fed dam over the last four years. A report of a site visit and investigation has been documented (DWR, 2001). It is difficult to make any further assessment in this area, as there are no observation wells and therefore no groundwaterlevel information. A drilling program has been established to install four wells during 2003 in areas where licensed wells are concentrated east of the Willunga Fault.
As can be seen in Fig. 6.2, rather than depicting well-defined clusters in the low- dimensional feature space, the feature extraction formed a densely packed cloud of WHPA realizations. In the case that a groundwater modeler has to select a specified number of rep- resentative scenarios in order to describe the overall structure of geological uncertainty, deter- mining the optimal number of clusters becomes not a trivial task. An option for partitioning, is to arbitrarily assign a number of clusters which subdivides the data set, and then to investigate whether the used amount of clusters helps to properly identify enough representative K-field scenarios. For instance, Fig. 6.2 shows the partition of the data cloud using 100 clusters, high- lighting in red the medoid of each cluster. Note that most of the selected scenarios are located at the center of each two-dimensional projection. This is mainly an effect of the very high density of realizations in the center. Nevertheless, the cluster analysis was able to recognize ensemble realizations with extreme feature performances such as those with larger WHPA outlines (high
Hydrographs have been produced to examine the effects of land clearance, irrigation and the construction of the Noora Disposal Basin on the hydrogeology of the Noora area. Figure 6 shows the impact land clearance has on the water levels. The rise in watertable is caused by the clearance of deep-rooted native vegetation and replacement by shallow- rooted crops. This results in an increase in recharge, and therefore, a rise in the watertable. BKP 11 (unit number 7029-33) shows an increase of 20 mm/y since 1973, while the water level in bore BKP 9 (7029-34) has not shown any significant increase since monitoring began in 1974. This well is close to the discharge area and also has a shallow depth to water. Therefore, the amount of recharge it receives is counteracted by discharge through evapotranspiration (hence, there is virtually no change in water levels). Irrigation processes lead to accessions of drainage water to the watertable. Figure 7 demonstrates this effectively with MTH 3 (7029-17) showing a water level increase of 20 mm/y since 1973.
Discovered in 1986, Movile Cave is a peculiar groundwater ecosystem sustaining abundant and diverse invertebrate communities. Isolated from the surface since preglacial times, the cave lacks input of allochthonous photoautotrophically based food. Instead, metazoan life in Movile Cave entirely depends on in situ chemoautotrophic production. Chemoautotrophic microbial mats floating on a cave pond of thermomineral, highly sulphidic and methanic water are inhabited by dense populations of five bacterivorous nematode species and a predacious copepod species. We experimentally simulated the unique physicochemical conditions of Movile Cave in order to develop a model system allowing laboratory investigation of the mat community. By manipulating the atmosphere in enclosures set atop the thermomineral water, we created hypoxic conditions that permitted the development of floating microbial mats. Both in the laboratory and the cave itself, these cultivated mats were quickly colonized by Movile’s highly adapted invertebrates. The nematode community structure was monitored for one year and strong fluctuations in the relative importance of individual species were observed. These fluctuations also characterized samples of native mat material and may reflect a succession of decreasing food conditions caused by the aging of the mats. However, previous reports on the occurrence of nematodes surviving and reproducing under complete anoxia could not be confirmed. Under truly anoxic conditions, neither mats nor nematodes developed. Successful simulation of the hypoxic cave habitat under laboratory conditions offers new possibilities to investigate the functioning of Movile’s ecosystem. The possibility that Movile Cave is not as isolated from the surface as previously assumed is discussed regarding the first report of a presumably epigean gnat in the cave.
Furthermore, cooperation on the use of transboundary aquifers is hampered by insufficient knowledge and a poor understanding of aquifer behaviour (recharge areas, flows, pollution, etc.). Due to this knowledge gap, the ripar- ians can not always be sure (1) whether their country form part of the groundwater basin, (2) whether they thus have a stake or an interest in trans- boundary groundwater cooperation, and (3) what exactly is at stake for their country, i.e. how high the costs of non-cooperation (or the benefits of coop- eration respectively) will be. This uncertainty often prevents cooperation: the parties can determine neither the costs nor the benefits of cooperation and non-cooperation. Only in very obvious cases is it possible to measure such factors and to identify the costs of present overdrafting. The countries which have succeeded in doing so for their respective basins are naturally the forerunners of cooperative groundwater management in Africa. Tunisia is such a case: it is already experiencing the impact of overextraction and depends heavily on groundwater use. Realizing that non-cooperation will involve major costs down the road, it has pushed for the establishment of transboundary cooperation mechanisms and research initiatives.
The pH is known to be a major factor influencing Cd mobility (Anderson and Christensen, 1988). While Cd is immobile in oxide and carbonate minerals under alkaline and neutral conditions, it can become mobile in acidic waters, due to dissolution of its host mineral. Thus far, there has been no large-scale study that investigated the behavior of Cd in groundwater with respect to pH. The groundwaters in the study area provided a range of pH values between 3.5 and 8.5, which is caused by the abundance of different natural areas and land use units influencing the groundwater composition. The occurrence of Cd above 0.5 µg/L was mostly found at a narrow range of pH values between 4.5 and 5.5. Thus, a pH-controlled Cd solubility was not likely for a major part of the studied groundwaters because the highest frequency of observations above the detection limit was observed at a pH around 7 (Figure 4.3). Groundwater samples with Cd concentrations exceeding the threshold value of 0.5 µg/L, however, occurred in a pH range where Cd sorption is inhibited (Spark et al., 1995). This was particularly in the Geesten areas, which are characterized by fast water infiltration and hence lower bicarbonate concentrations resulting in a limited buffer capacity. Land use in the Geesten also affected Cd mobility. Forest soils, for example, that mainly occurred in the Geesten showed elevated concentrations in organic matter. However, there was no correlation between Cd and DOC in the data set, although Cd-organic complexes are considered very stable (Krishnamurti and Naidu, 2003). One explanation of this lack of correlation could be dissolved organic matter can reduce Cd sorption at lower pH due to competition of organic matter and protons with Cd for sorption sites (Sprynskyy et al., 2011), hence, adding Cd and removing organic matter from groundwater. On the other hand, Cd becomes more immobile at a pH above 6, due to sorption by minerals such as Fe(III) hydrous oxide and precipitation as CdCO 3 and Cd(OH) 2 (Carrillo-Gonzalez et al., 2006), but this occurred mainly in the tidal wetlands, lowlands, and uplands hydrogeological units. In contrast, woodland and farmland induced acidification can lower the pH of groundwater, e.g., due to nitrification of NH 4 derived from fertilizers (Mollema et al., 2015), and thus keep Cd in solution.
First of all, the run options in GMS had to be defined. The type of simulation was set to flow only steady state. As a solver, the pointwise iterative matrix solver was selected. The other options like weighting factor or quadrature selection were left as default. The initial conditions in GMS were set to cold start with a pressure head computed from the constant heads as they were set as boundaries. The iteration parameters were left as default. In the fluid properties, 1000kg/m³ was set as density of the water. The viscosity was set to 4.68 kg/m/hr. The compressibility of water was set to 3.410 -17 m-hr²/kg and the acceleration due to gravity was set as 1.2710 8 m/hr². The boundaries were assigned as discussed in chapter 5.3.4. According to LIN H.J. ET AL. (1997), the variable boundary conditions were used for the groundwater recharge. Later on during calibration, they were changed to a constant flux boundary because no unsaturated zones were modelled. The material properties for the beginning of the calibration were taken out of literature (EL-NASER (1991), KHDIER (1997), JICA (1995)) (Tab. 17).
For the karstic aquifer, using the same method may produce uncertainties, since the groundwater flow is in both the matrix and the karstic conduits, so the flow does not have a specific pattern. This can be very important in the case that water that infiltrates is not directed into the drill, on the contrary, it is stored in cavities, as mentioned earlier (§ 2.3.4). Nevertheless, the chosen method can still be used in such an aquifer to get a first estimation of the rechargesince, generally speaking, it only takes under consideration the amount of water that reaches the water table. The specific storativity for the matrix of the karstic aquifer, as seen in the analysis of the pumping test data, is 0.001661 m -1 and with a minimum thickness of 50 m and a specific yield of 5 % for such aquifers (Ford and Williams, 2007), the estimated recharge is 38 % of the precipitation amount. The figure may seem high but in such areas, where the is practically no surface runoff and the karstification gives a path for water to further infiltrate into the subsurface, recharge can be a substantial amount of the precipitation.
Difficulties in monitoring groundwater extraction caused groundwater regulations to fail worldwide. In two counties in north-west China local water authorities have installed smart card machines to monitor and regulate farmers’ groundwater use. Data from a household survey and in-depth interviews are used to evaluate the effectiveness of the different regulatory institutions implemented with help of the smart card machines. In the given context, groundwater quota is more effective in curbing farmers’ groundwater use than tiered groundwater pricing. The study shows that the usefulness of smart card machines for water saving varies depending on their embedding in a certain societal context and related regulatory institutions.
is used that considers climatic conditions (P, E p ), maximum plant available soil water (W a ), water supply by capillary rise from groundwater table, and the simultaneity of water and energy supply. An attempt was made to consider the effect of anaerobiosis on actual evapotranspiration.
For any experiment, sufficient temporal and spatial sampling with reference to the desired outcome is funda- mental. This also applies to field scale measurement systems deployed for hydrogeology. The hydraulics at coastal margins has significant differences compared to most hydrogeological settings. In Part 6, we will compute the dis- tribution of Darcy flow velocity across the seawater interface and will later consider implications for the type of monitoring systems that may be suitable for characterising this highly dynamic setting. Also, we suspect that methods for measuring groundwater flow velocity itself may present useful and currently under-utilised pathways to characterising shallow high-quality coastal aquifers for both research and aquifer management purposes.