Fresh Water Lens Persistence and Root Zone Salinization Hazard Under Temperate Climate

Abstract

In low lying deltaic areas in temperate climates, groundwater can be brackish to saline at shallow depth, even with a yearly rainfall excess. For primary production in horticulture, agriculture, and terrestrial nature areas, the fresh water availability may be restricted to so-called fresh water lenses: relatively thin pockets of fresh groundwater floating on top of saline groundwater. The persistence of such fresh water lenses, as well as the quantity and quality of surface water is expected to be under pressure due to climate change, as summer droughts may intensify in North-West Europe. Better understanding through modelling of these fresh water resources may help anticipate the impact of salinity on primary production. We use a simple model to determine in which circumstances fresh water lenses may disappear during summer droughts, as that could give rise to enhanced root zone salinity. With a more involved combination of expert judgement and numerical simulations, it is possible to give an appraisal of the hazard that fresh water lenses disappear for the Dutch coastal regions. For such situations, we derive an analytical tool for anticipating the resulting salinization of the root zone, which agrees well with numerical simulations. The provided tools give a basis to quantify which lenses are in hazard of disappearing periodically, as well as an impression in which coastal areas this hazard is largest. Accordingly, these results and the followed procedure may assist water management decisions and prioritization strategies leading to a secure/ robust fresh water supply on a national to regional scale.

Irrigation and Drainage in Agriculture: A Salinity and Environmental Perspective

“…Taking into account the often erratic variability of weather [33], recently the salt accumulation in the root zone was investigated, considering that root zone salinity levels respond fast to the water quality of incoming fluxes (rainfall, irrigation, capillary rise). In general, say in 10 years, the root zone concentration attains a dynamic equilibrium with rain, irrigation water, and groundwater quality.…”

Climate Proof Fresh Water Supply in Coastal Areas and Deltas in Europe

“…These papers are functional in -representing and demonstrating a wide range of tools to assess risk of fresh water shortage under climate change at both local (Stofberg et al, 2016) and regional scale (Stigter et al, 2015, Giannikopouloua et al, 2015, and Iglesias et al, 2015, -providing practical examples of how to systematically compare different adaptation strategies (Giannikopouloua et al 2015) and socio-economic development scenarios (Stigter et al, 2015). -exploring novel methods to develop resilient, robust and flexible adaptation plans (Thissen et al, 2015) to account for a range of future developments (Stigter et al, 2015) -and showing that adoption of new technologies such as presented by Zuurbier et al, 2016 and inventoried by Iglesias et al.…”

“…The authors argue that prolonged SWT testing in the current pilots, replication of SWT in other areas worldwide, and the development of technical and non-technical support tools are required to facilitate potential end-users in investment decision making and SWT implementation. Stofberg et al, 2016 provide an extensive overview of analytical modeling tools to simulate and quantify the dynamics of fresh water lenses and its effects on the root zone of crops or the natural vegetation. These tools help appraising the hazard of fresh water lenses disappearing from the Dutch coastal regions.…”

Dynamics of rainwater lenses on upward seeping saline groundwater

“…Water management often takes place on a regional rather than a field scale, as the latter is often small compared to water management units. Upscaling of local lens systems behaviour to a regional water system, based on the physical relations found has been brought a step closer, and some of this upscaling was already investigated by Pauw et al (2015) and Stofberg et al (2016).…”

“…The lens has then (temporarily) disappeared. The occurrence of such situations was lately investigated by Stofberg et al (2016). Therefore, apart from the characteristics of the lens, the situations in which the effect of saline seepage on vegetation is significant need to be characterized.…”