Anticipating the effects of groundwater withdrawal on seawater intrusion and soil settlement in urban coastal areas

Abstract

Intensive pumping in urban coastal areas is a common threat to water resource quality due to seawater intrusion. In those areas where subsurface water resources are not usually used for human consumption or irrigation, intensive pumping is associated with other activities like the lowering of the water table necessary to support underground structures and building foundations. This activity also increases the likelihood of soil settlement that affects building stability and the corrosion of concrete structures due to groundwater salinity. Under these circumstances, the awareness of a certain municipality (Calonge, NE Spain) of the potential effects of groundwater withdrawal upon foundations has led to an integrated approach to anticipate seawater intrusion related to urban development. Geological mapping and correlation of borehole logs, electrical resistivity tomography, and hydrochemical data provide comprehensive knowledge of the geology and hydrogeology of the area and act as screening tools necessary to discern the influence of hydrological processes in coastal areas. Developing Strack's analytical solution, new comprehensive, dimensionless expressions are herein derived to determine the critical pumping rate necessary to prevent seawater intrusion, as well as to reproduce the evolution of the wedge toe and the water table stagnation point under different withdrawal rates. Furthermore, the Dupuit-Forchheimer well discharge formula allows the estimation of the effects of the water table lowering due to such critical pumping in the surrounding building foundations. Field data from the Calonge coastal plain illustrate this approach and provide assessment criteria for future urban development and planning. Temperature (T) is given in C; electrical conductivity (EC) is in mS/cm; and alkalinity (as HCO 3 ), dissolved oxygen (DO) and other major elements/ compounds are in mg/l. Errors based on % ionic balance. *Seawater composition according to a Mediterranean Sea sample from the Costa Brava region (Kruse and Mas-Pla, 2009).

Stable Isotopes and Hydrochemistry Approach for Determining the Salinization Pattern of Shallow Groundwater in Alluvium Deposit Semarang, Central Java

“…Another effect of excessive groundwater extraction is seawater intrusion (Mas-Pla et al, 2013) which leads to groundwater salinization. In recent years, increasing phenomena of groundwater salinization were found in several locations in Semarang area, mainly in residential areas and several industrial areas in the northern part, i.e.…”

Large Scale Electrical Resistivity Tomography Survey Correlated to Hydrogeological Data for Mapping Groundwater Salinization: A Case Study from a Multilayered Coastal Aquifer in Rhodope, Northeastern Greece

“…In certain occasions (Wilson et al, 2006), the ERT technique was used in order to supplement and clarify the results of initially executed one dimensional VES in the same region. The efficiency of the ERT technique in a variety of inshore geological settings is demonstrated by various researchers, including coastal alluvial aquifers (Abdul Nassir et al, 2000;Morrow et al, 2010;Ebraheem et al, 2012;Mas-Pla et al, 2012), coastal deltaic deposits (Maillet et al, 2005;Martínez et al, 2009;Gurunadha Rao et al, 2011), or inland saline environments, e.g., in the Okavango Delta, Botswana (Bauer et al, 2006), in the Dead Sea, Jordan aquifer (Batayneh, 2006), and in Querenca-Silves, south Portugal (Leitão et al, 2014). These authors have utilized various array configurations and electrode spacing intervals, and showed that the method is able to provide a good correlation between specific resistivity values and hydrogeological properties, and thus, to calculate formation factors (Archie, 1942) for the separate aquifer units, by combining groundwater electrical resistivity measurements and bulk formation resistivity distribution.…”

District-scale numerical analysis of settlements related to groundwater lowering in variable soil conditions

“…Many urbanised areas worldwide have subsided due to the presence of highly compressible soils (namely "soft soils") (Erkens et al 2015;Herrera-Garcia et al 2021). The occurrence, magnitude, and distribution of ground settlements are highly influenced by soil variability (Breysse et al 2005;Elkateb et al 2003;Marache et al 2009;Popescu et al 2005) as well as the groundwater regime (Guzy et al 2020;Mas-Pla et al 2013;Modoni et al 2013;Shahrian et al 2013). This is the case in many delta countries such as the Netherlands, in which shallow subsurface layers consist of fluvial and coastal lowlands of the Holocene age comprising recent unconsolidated sedimentary deposits (Dufour 2000;van der Meulen et al 2013).…”