Determining the hydrologic response of greenhouses in the Westland

By Kasper Keizer

Precipitation is the main source of water for crops in the greenhouses in the Netherlands. The precipitation on the roof of a greenhouse is collected in a fresh water basin. The water in the basin gives the horticulturist (greenhouse farmer) the certainty to be able to irrigate his crops for several weeks. It is for this reason that the horticulturist endeavours to keep the basin as full as possible. When the basin is completely filled the surplus water overflows into the surface water around the greenhouse.

Keeping these surface waters at target level is the responsibility of the Water Boards. In the Westland, one of the world’s largest greenhouse areas, the surface waters are managed by the Water Board of Delfland.

The exact volume, the exact time and the course in time of the overflows from the basins at greenhouses are not well known to the Water Board of Delfland. The absence of this knowledge, combined with the fact that due to the climate change it will rain harder and more often, makes it highly desirable to gain more insight into the hydrologic response of the greenhouses (in particular the overflows into the surface waters).

The aim of this thesis is to determine the hydrologic response of some specific greenhouses and create a model to predict the hydrologic response for greenhouses in general. With these insights it is the aim to if possible adjust current assumptions and models. The insights gained in this thesis will contribute to allow the Water Board of Delfland to continue to properly manage the surface water levels in the Westland in the future.