Critical Zone Hydrology Group

Behaviour of fresh water lenses on a parcel scale in relation to field drainage systems and the capillary flow under current and future climatic conditions

Supervisors and collaborators:

• J. Groen - VU University

Duration: 2008 -
Funding: Research programme Living with Water, research programme Knowledge for Climate, Acacia Water

Research background

In many coastal and arid regions field drainage is applied to control groundwater levels but also salinities of groundwater and unsaturated zone. In coastal areas with upward seepage of groundwater, notably the Dutch polders, drainage systems intercept brackish groundwater and allow rainfall to form shallow fresh rainwater lenses. These lenses are crucial for sustaining crop growth. Likewise drainage systems in semi-arid regions restrain the groundwater from rising to close to the surface, where evapotranspiration would lead to salinization. In the past improper or lacking field drainage made extensive areas turn into saline wastelands, as the rising groundwater resulting from irrigation losses and deforestation was not curbed.
Design of field drainage systems are generally based on rules of thumb or, at best, on analytical models for saturated groundwater flow. However these underlying conceptual models do not include the intricacies of water and salt transport in the dynamic zone from the upper groundwater to the surface. The behaviour of the hydrological boundary layer is complex. 2D-resistivity soundings of croplands on clay soils displayed the presence of fresh water lenses between tile drains and upconing of brackish groundwater near the drains. The thicknesses of the lenses vary from of few decimeters to meters, have a strong seasonal pattern.
The objective of my study is to get more insight in the behaviour of fresh water lenses in relation to field drainage systems and the capillary flow. With respect to the latter particular attention is paid to incursion of brackish water into the root zone.

Publications

• Velstra, J., J. Groen and K. de Jong (2011). Observations of salinity patterns in shallow groundwater and drainage water from agricultural land in the northern part of the Netherlands. Irrigation and Drainage 60: 51-58.
• Velstra, J. en J. Groen en M. Boomgaard (2010). Mogelijkheden voor beperking van inlaatwater in polders. H2O jrg 43, nr 17.
• Velstra, J., J. Oosterwijk and J. Groen (2010). Impact of climate change on salinization during dry periods in Dutch polders and necessity of adaptation strategies. HydroPredict proceedings.
• Velstra, J. and M. ter Voorde: editors. (2009). Overzicht van de huidige kennis en kennishiaten op het gebied van verzilting in Nederland. STOWA uitgave 45.
• Zaadnoordijk, WJ, J. Velstra, A.J.J. Vergroesen en H. Mankor (2009). Groot Mijdrecht: inzicht in functioneren wellen. Stromingen jrg 15, nr 2.
• Velstra, J., A. de Vries (2008). Een nieuwe kijk op verzilting biedt perspectief voor het zoetwater tekort. H2O, jaargang 41(2008), nummer 22, pagina 20-21.
• Huitema, D., S. Brouwer, J. Velstra, M. Hoogmoed (2007). Verzilting: beleidsprobleem in wording. H2O, jaargang 40(2007), nummer 16, pagina 18-19.
• Paulissen, M.P.C.P., E.P.A.G. Schouwenberg, J. Velstra, en G.W.W Wamelink (2007). Hoe gevoelig is de Nederlandse natuur voor verzilting? H2O, jaargang 40(2007), nummer 18, pagina 40-44.
• Velstra J. and T. Kleinendorst (2006). Using a groundwater model to identify groundwater systems associated with ecosystems: Application for risk assessment, monitoring and effectiveness of measures. HydroEco 2006, Proceedings.
• Heimovaara, T., J. Velstra, H. Keijzer (2004). Using inverse modelling in combination with a regional groundwater model to visualize spreading of multiple plumes. FEM_MODFLOW conference 2004: Solving Groundwater Problems Proceedings
• Groen, J., Velstra, J. and Meesters, A.G.C.A., (2000). Salinization processes in paleowaters in coastal sediments of Suriname: evidence from 37Cl analysis and diffusion modeling. Journal of Hydrology 234, 1-20.