Assessing impacts of climate change, sea level rise, and drainage canals on saltwater intrusion to coastal aquifer

Abstract

Groundwater abstraction from coastal aquifers is vulnerable to climate change and sea level rise because both may potentially impact saltwater intrusion and hence groundwater quality depending on the hydrogeological setting. In the present study the impacts of sea level rise and changes in groundwater recharge are quantified for an island located in the Western Baltic Sea. The low-lying central area of the investigated part of the island was extensively drained and reclaimed during the second half of the 19th century by a system of artificial drainage canals that significantly affects the flow dynamics of the area. The drinking water, mainly for summer cottages, is abstracted from 11 wells drilled to a depth of around 20 m into the upper 5–10 m of a confined chalk aquifer, and the total pumping is only 5–6% of the drainage pumping. Increasing chloride concentrations have been observed in several abstraction wells and in some cases the WHO drinking water standard has been exceeded. Using the modeling package MODFLOW/MT3D/SEAWAT the historical, present and future freshwater-sea water distribution is simulated. The model is calibrated against hydraulic head observations and validated against geochemical and geophysical data from new investigation wells, including borehole logs, and from an airborne transient electromagnetic survey. The impact of climate changes on saltwater intrusion is found to be sensitive to the boundary conditions of the investigated system. For the flux-controlled aquifer to the west of the drained area only changes in groundwater recharge impacts the freshwater–sea water interface whereas sea level rise does not result in increasing sea water intrusion. However, on the barrier islands to the east of the reclaimed area, below which the sea is hydraulically connected to the drainage canals, and the boundary of the flow system therefore controlled, the projected changes in sea level, groundwater recharge and stage of the drainage canals all have significant impacts on saltwater intrusion and the chloride concentrations found in abstraction wells

Assessing impacts of sea level rise on seawater intrusion in a coastal aquifer with sloped shoreline boundary

“…The effects of pumping resulting in lowering of groundwater level are also 17 considered together with the dynamic variation of sea level. The results show that the rate and 18 the amount of SWI are considerably greater in aquifers with flat shoreline slopes compared 19 with those with steep slopes. Moreover, a shorter period of time is required to reach a new 20 steady state condition in systems with flatter slopes.…”

“…SLR could cause problems such as impeded drainage, wetland loss (and 15 change), erosion and inundation of the land-surface and also saltwater intrusion (Bricker,16 2009; FitzGerald et al, 2008;Nicholls, 2010Nicholls, , 2015. These changes in ecosystem properties 17 and processes have several direct socio-economic impacts on a wide range of sectors and 18 issues (Nicholls, 2015;Sušnik et al, 2015). Saltwater intrusion threatens the quantity and 19 quality of groundwater resources.…”

Integrating aerial geophysical data in multiple-point statistics simulations to assist groundwater flow models

“…From literature, rarely have aerial geophysics quantitatively aided the development of groundwater flow models. Examples exist that account for remote sensing (Elsheikh et al 2011;Okazaki et al 2011), time domain electro-magnetics (Andersen et al 2013;Friedel et al 2012;Gondwe et al 2010;Rasmussen et al 2013;Sulzbacher et al 2012) and magnetics (Brunner et al 2007) for a variety of applications. In this last study, Brunner et al (2007) undertook several case studies to determine the location of faults and dykes for groundwater modelling.…”

Comparison of the AVI, modified SINTACS and GALDIT vulnerability methods under future climate-change scenarios for a shallow low-lying coastal aquifer in southern Finland

“…Luoma and Okkonen 2014;Luoma et al 2013;Oude Essink 1999Barlow 2003;Pulido-Leboeuf 2004;Oude Essink et al 2010;Rasmussen et al 2013;Ferguson and Gleeson 2012;Ataie-Ashtiani et al 2013). These events will presumably be accelerated by the changing climate, including changes in precipitation, temperature and groundwater recharge, as well as sea-level rise and an increasing frequency of storm surges (IPCC 2000(IPCC , 2007Nicholls et al 2007).…”