In May 2017, the Rijnland Water Authority started using measuring equipment that helps provide better insight into the impact of climate change on water management. This involves three Eijkelkamp Smart Lysimeter measuring stations, which in addition to evapotranspiration data also provide data about the amount of precipitation, wind and soil moisture.
“Why did we acquire three Eijkelkamp Smart Lysimeter stations?” Jan Willem van Kempen, Water Level Manager, and René van der Zwan, Advisor Policy and Research, both employed by the Rijnland Water Authority, explain: “On the one hand, our work involves operational water level management, and on the other hand it is clear that water level management in part is under pressure due to climate change. Climate change is a very high priority for the Rijnland Water Authority.”
“We use an automated decision support system for our water level management operations. This system is supplied with a wide range of measurement information, including water levels and precipitation. The only key item into which we do not have good insight is water evapotranspiration. In fact, this is a big question mark for us, especially after dry and during wet periods. Up until now, we used models to obtain this information. But how good is your model and, furthermore, it requires a certain period of synchronisation. Enough for us to ask ourselves, how do we complete the water balance equation?”
René van der Zwan - Advisor Policy and Research, Rijnland Water Authority
“We contacted Eijkelkamp Soil & Water because we wanted to acquire a practical lysimeter station rather than a large 20 x 5 metre concrete reservoir. The latter is not easy to install and is difficult to maintain. Furthermore, Eijkelkamp Soil & Water had already installed a surface water monitoring network for us. We are going to use the web portal designed for this purpose for the evapotranspiration data as well.”
“Together with Eijkelkamp Soil & Water, we ultimately installed a lysimeter measuring station at three sites: in Noordwijkerhout on sandy soil, in Woubrugge on clay soil and in Reeuwijk on peat soil. With these three sites we are covering off our three main soil types and together with a meteorological station, and soil moisture and groundwater measurements we now have a unique combination of measuring stations. As such, the Rijnland Water Authority has taken a leading role in water management in the Netherlands.”
“It is interesting to see that the ‘Netherlands Inc.’ is now looking at our initiative from a variety of angles. In addition, we are receiving lots of requests to be allowed to view the results as we progress. In the context of big data, we are definitely interested in sharing our information, just like we do with water levels.”
Jan Willem van Kempen - Advisor Policy and Research, Rijnland Water Authority
“One of the meters is located in Reeuwijk. A project is currently underway here for the flexible water level management of the Reeuwijkse lakes. We noticed that there is a tremendous lack of knowledge among residents concerning the effect of evapotranspiration on groundwater levels. At one time, we carried out a project together with residents designed to measure surface water levels and groundwater levels to provide insight into what causes the differences. The surface water level fluctuated within a range of 5 to 10 cm. By contrast, a few metres away, the groundwater fluctuated between 50 to 60 cm. This completely mystified residents. Until you use an evapotranspiration and a precipitation meter to show them how many mm of rain fell and how many mm evaporated from the soil. Ultimately, we are getting a better picture of the water demand in our system under dry conditions. Groundwater Behaviour When it rains, does this immediately result in runoff or is the water first stored within the soil?”
“Another example. We are currently working on the renovation of a pumping station, as a result of which, we are losing some capacity. To offset this loss, you can attempt to anticipate future conditions. The drawback of doing this, most certainly in the summer, is that you could end up pumping out valuable water that you might very well need a few days later. At that point, it may almost be impossible to get it back, particularly when the Rhine or Moselle rivers are low and the main system has become brackish. But when you know what the groundwater level is and the soil has a very high storage capacity, you do not need to anticipate a rain shower and pump out valuable water. This way, we will be able to engage in smart water level management in the near future.”
“A current topic of debate is land subsidence. People sometimes are suspicious of our actions when we allow the water level in our ditches to drop too much. However, when you know how much water evaporates and what the groundwater level is, you see that the effects of the Water Authority’s actions on land subsidence are not all that great. Precipitation is far more important than the water in the ditches. In that sense, the evapotranspiration data is going to help us in the debate concerning land subsidence. We have to start looking at this issue in different ways.”
“There is a farmer who lives near Leiden and who has installed drainage throughout his land. He is actively pumping water from the ditch into his land in order to counteract land subsidence. He is keeping us informed of the outcome in order to assess the effect of this. It is becoming evident that increasingly more farmers are becoming interested in acquiring measurement data relating to soil moisture and evapotranspiration.”
“For example, a farmer in Woubrugge, where we have an Eijkelkamp Smart Lysimeter station, was working on a business plan for acquiring more measuring equipment. Before he starts harvesting his potatoes in the fall, he first measures the soil’s moisture to determine whether the soil is too dry. If so, he can still harvest his potatoes, but he will also pull out too much clay. He therefore sprinkles his land before harvesting. Except now, he is also faced with climate change. Because if a heavy rainfall is approaching, you will want to avoid sprinkling. This forces the farmer to operate at the cutting edge and this is where evapotranspiration information can be of help. It is good to see that the demand for data from this sector is also increasing.”
The Rijnland Water Authority has been providing for safe dikes, clean and healthy water in lakes and ditches, and for balanced water levels, since 1255. Furthermore, it also purifies the wastewater generated by all of the households and companies in its area of operations. This area stretches from IJmuiden to Gouda and from Wassenaar to Amsterdam. It comprises 1,175 km2 and over 1.3 million inhabitants.