Presentations 2016

The Netherlands hosts a well-developed agricultural sector that largely relies on an almost guaranteed availability of fresh water from surface water or ground water sources. This business strategy is at risk of failure, however, because socio-economic developments and climate change will lead to prolonged periods of water scarcity due to increasing water demand and decreasing water availability. In order to secure sufficient agricultural water supply to maintain current crop yields in future, water managers seek for measures to mitigate water scarcity. In search for these measures, particular interest is exhibited to the implementation of measures for improving regional self-sufficiency in water demand by re-using waste water as a source for agricultural crop irrigation. Major challenge for implementation of this strategy is the development of a cost-effective infrastructure for equal distribution and supply of waste water across agricultural fields. In this study, we investigated whether such infrastructure can be provided by sub-irrigation systems. Sub-irrigation is a parcel-scale, subsurface technique for water distribution and supply across agricultural fields. It consists of a network of subsurface drains, interconnected through a collector tube, and connected to an inlet control pit for supply water to enter the drainage system. Sub-irrigation may be more efficient compared to classical, above ground irrigation techniques, as evaporation losses are prevented and vast agricultural fields can be irrigated in equal or manageable amounts. Moreover, when irrigating from waste water, sub-irrigation prevents crop leaves from being exposed to the waste water, and its solutes, which can be harmful for the crop itself or lead to public health risks. A possible disadvantage of sub-irrigation with waste water is that sub-optimal water quality may speed up clogging of drain tubes used to distribute and supply irrigation water equally over the parcel. This would require more regular and intense maintenance, causing additional costs. To foresee and prevent costs associated with clogging of the drain tubes, we employed experimental research on two soil columns that were supplied with waste water from the Bavaria Beer Brewery. To this purpose, two undisturbed soil columns (1.0 x 0.5 x0.5 m) were collected from an agricultural field by gently pressing a perforated casing made of stainless steel into the soil. After installing perforated bottom plates, a drain, 6 cm in diameter, was installed along the longitudinal axis of each soil column. The soil columns, cased in perforated stainless steel, were installed in containers filled with course-grained sand, and attached to inflow and outflow containers with adjustable water levels. Head differences over and within the soil column and outflow fluxes were measured hourly using pressure sensors. Based on these experimental data and supporting Hydrus 2D simulations we quantify irrigation and clogging rates and translate the results to field scale application. With this poster, we present the method and results of a series of column experiments and seek for discussion about additional experimental research on measures to prevent clogging of sub-irrigation systems when using waste water.