The Raam regional soil moisture monitoring network in the Netherlands

Abstract

Abstract.We have established a soil moisture profile monitoring network in the Raam region in the Netherlands. This region faces water shortages during summers and excess of water during winters and after extreme precipitation events. Water management can benefit from reliable information on the soil water availability and water storing capacity in the unsaturated zone. In situ measurements provide a direct source of information on which water managers can base their decisions. Moreover, these measurements are commonly used as a reference for the calibration and validation of soil moisture content products derived from earth observations or obtained by model simulations. Distributed over the Raam region, we have equipped 14 agricultural fields and 1 natural grass field with soil moisture and soil temperature monitoring instrumentation, consisting of Decagon 5TM sensors installed at depths of 5, 10, 20, 40 and 80 cm. In total, 12 stations are located within the Raam catchment (catchment area of 223 km 2 ), and 5 of these stations are located within the closed sub-catchment Hooge Raam (catchment area of 41 km 2 ). Soil-specific calibration functions that have been developed for the 5TM sensors under laboratory conditions lead to an accuracy of 0.02 m 3 m −3 . The first set of measurements has been retrieved for the period 5 April 2016-4 April 2017. In this paper, we describe the Raam monitoring network and instrumentation, the soil-specific calibration of the sensors, the first year of measurements, and additional measurements (soil temperature, phreatic groundwater levels and meteorological data) and information (elevation, soil physical characteristics, land cover and a geohydrological model) available for performing scientific research. The data are available at https://doi.org/10.4121/uuid:dc364e97-d44a-403f-82a7-121902deeb56.

Anatomy of the 2018 agricultural drought in The Netherlands using in situ soil moisture and satellite vegetation indices

“…The Raam and Twenthe soil moisture networks in The Netherlands were originally installed as validation sites for satellitederived data products (Benninga et al, 2018;Dente et al, 2011). The Raam network faces-by Dutch standards and in comparison to the Twenthe network-substantial water shortages during normal summers (Benninga et al, 2018). This can be mainly attributed to the mostly sandy soils in the Raam network, whereas the Twenthe network is located in an area with sandy to more loamy soils.…”

Towards Estimating Land Evaporation at Field Scales Using GLEAM

“…In situ measurements of surface soil moisture (i.e., sensors installed at a maximum depth of 10 cm, corresponding to the lower level of the first soil layer in GLEAM) are obtained from the database of the International Soil Moisture Network (ISMN) [65,66], and the regional soil moisture network in the Raam catchment [67]. Data are processed using a similar procedure as for the eddy-covariance data, except for the rain mask, which is not applied.…”

“…Soil moisture validation sites, on the other hand, are clustered in the Eifel area in west Germany, and the Raam catchment in the east of The Netherlands. The latter is an intensively-measured, medium-scale 223 km 2 catchment where data from 14 soil moisture sensors are available [67]. Also note that measurements of both surface soil moisture and evaporation are available at three sites ( Table 2 and Figure 1).…”

Validation of SMAP L2 passive-only soil moisture products using <i>in situ</i> measurements collected in Twente, The Netherlands

“…In the case of the in situ measurements, the probes have an 4 cm influence zone (e.g. Benninga et al 2018) and, thus, provide information for the 1 -9 cm soil layer, while the LHM root zone layer has for the Twente region a nominal depth of 40 cm. This explains the overestimation by LHM in the summer and partly the underestimation in the winter as the larger soil reservoir takes longer to fill up/to deplete, and has also more direct interactions with the groundwater.…”

“…In the latter two, dry spells were ended by a sequence of substantial rain events that exposed the disparity in sampling depth between SMAP and the in situ sensors. Indeed, the in situ sensors of Twente network installed at a 5 cm soil depth effectively monitor the 1 -9 cm soil layer below the surface (Benninga et al 2018), while SMAP's sampling depth is generally considered to be shallower and depends on the soil moisture content (e.g. Colliander et al 2017, Zheng et al 2019.…”