Evaluation of the ZigBee based wireless soil moisture sensor network SoilNet

A remaining challenge in hydrology is to explain the observed patterns of hydrological behaviour over multiple spacetime scales as a result of interacting environmental factors. The large spatial and temporal variability of soil water content is determined by factors like atmospheric forcing, topography, soil properties and vegetation, which interact in a complex nonlinear way (e.g. Western et al., 2004). A promising new technology for environmental monitoring is the wireless sensor network (Cardell-Oliver et al., 2005). The wireless sensor network technology allows the real-time soil water content monitoring at high spatial and temporal resolution for observing hydrological processes in small water-sheds (0.1-80 sqkm). Although wireless sensor networks can still be considered as an emerging research field, the supporting communication technology for low cost, low power wireless networks has matured greatly in the past decade (Robinson et al., 2008). Wireless environmental sensor networks will play an important role in the emerging terrestrial environmental observatories (Bogena et al., 2006), since they are able to bridge the gap between local (e.g. lysimeter) and regional scale measurements (e.g. remote sensing). This paper presents a first application of the novel wireless soil water content network SoilNet, which was developed at the Forschungszentrum Jülich using the new low-cost ZigBee radio network

Sensor-to-sensor variability of ECH2O EC-5, TE and 5TE sensors used for wireless sensor networks

Towards an improvement of measurement accuracy for the low-budget soil water content sensors ECH2O EC-5, TE and 5TE used in the wireless sensor network SoilNet, the application of a sensor-specific calibration procedure based on dielectric standard liquids reduce the RMSE of approximately 0.010 to 0.015 cm^3 cm^-3 in high soil water content range

Fuentes de variabilidad que intervienen en la medicion de contenido de agua en el suelo en parcelas de manzano regadas por goteo

Comunicación presentada al XXXVII Congreso Nacional de Riegos, celebrado en Don Benito del 4 al 6 de Junio de 2019 y organizada por la Asociación Española de Riegos y Drenajes y la Universidad de ExtremaduraEl riego por goteo aplica el agua en el suelo de manera eficiente, reduciendo la superficie mojada y aportando el agua cerca de las raíces. Pero ello determina una distribución de la humedad del suelo heterogénea, que complica la monitorización con sensores. La finalidad de este trabajo es caracterizar la incertidumbre que aportan distintas fuentes de variabilidad implicadas en la medición con sensores de tipo capacitivo en un cultivo de manzanos regado por goteo. Para ello se ha analizado (1) cómo varía en condiciones reales de campo la extensión superficial de los bulbos húmedos y su centrado respecto a los goteros, (2) el ajuste en laboratorio, para el suelo objeto de estudio, entre la permitividad dieléctrica y el contenido relativo de agua, que es el principio en que se basan los sensores de tipo capacitivo, y (3) la respuesta individual de los sensores Decagon 10HS a medios de permitividad dieléctrica conocida. Los resultados muestran que, aun fijando la posición de los sensores en relación a los goteros, la mayor fuente de desviación entre mediciones del contenido relativo de agua en el suelo corresponde a la propia variabilidad de los bulbos húmedos (RMSE = 0.088 m3 m-3), mientras que la respuesta de distintos sensores individuales a la permitividad es muy repetitiva (RMSE = 0.003 m3 m-3). Un uso adecuado de sensores en condiciones de riego localizado deberá contemplar la variabilidad entre bulbos húmedos, tanto en la instalación de los sensores como en su interpretación.Drip irrigation applies water to the soil in an efficient way, reducing the wet surface and supplying water close to the root zone. However, it determines a heterogeneous distribution of water in the soil that complicates its monitoring with sensors. The purpose of this work was to characterize the main sources of uncertainty involved in the measurement with capacitive-type sensors in a drip-irrigated apple orchard. To that end, we analyzed (1) the variability in real field conditions of the extension and centering of wet bulbs, (2) the relationship in laboratory conditions, for the soil of interest, between dielectric permittivity and water content, which is the principle on which capacitive-type sensors are based; and (3) the response of individual sensors Decagon 10HS to different media of known electrical permittivity. The results show that, even at fixed positions relative to drippers, the largest uncertainties in the assessment of relative soil water content comes from the variability of the wet bulbs (RMSE = 0.088 m3 m-3), while the response of individual sensors to permittivity was very repetitive (RMSE = 0.003 m3 m-3) An adequate use of sensors under localized irrigation should consider the variability between wet bulbs, both in the installation of the sensors and in their interpretation.Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) (Proyecto RTA2013- 00045-C04-01 y FPI INIA), por el Fondo Social Europeo y por el Fondo Europeo de Desarrollo Regional (FEDER

Atmospheric deposition and precipitation are important predictors of inorganic nitrogen export to streams from forest and grassland watersheds: a large-scale data synthesis

Previous studies have evaluated how changes in atmospheric nitrogen (N) inputs and climate affect stream N concentrations and fluxes, but none have synthesized data from sites around the globe. We identified variables controlling stream inorganic N concentrations and fluxes, and how they have changed, by synthesizing 20 time series ranging from 5 to 51 years of data collected from forest and grassland dominated watersheds across Europe, North America, and East Asia and across four climate types (tropical, temperate, Mediterranean, and boreal) using the International Long-Term Ecological Research Network. We hypothesized that sites with greater atmospheric N deposition have greater stream N export rates, but that climate has taken a stronger role as atmospheric deposition declines in many regions of the globe. We found declining trends in bulk ammonium and nitrate deposition, especially in the longest time-series, with ammonium contributing relatively more to atmospheric N deposition over time. Among sites, there were statistically significant positive relationships between (1) annual rates of precipitation and stream ammonium and nitrate fluxes and (2) annual rates of atmospheric N inputs and stream nitrate concentrations and fluxes. There were no significant relationships between air temperature and stream N export. Our long-term data shows that although N deposition is declining over time, atmospheric N inputs and precipitation remain important predictors for inorganic N exported from forested and grassland watersheds. Overall, we also demonstrate that long-term monitoring provides understanding of ecosystems and biogeochemical cycling that would not be possible with short-term studies alone.publishedVersio

Toward Better Understanding of Terrestrial Processes through Long-Term Hydrological Observatories

Observation of hydrological processes has a long-standing tradition covering various climatic, hydrologic, geologic, and geomorphologic conditions. Hydrological observations are either organized in dedicated observatories focused on hydrology or within larger environmental observatories that address processes from the atmosphere to the groundwater. In this special section, we document hydrological observations currently conducted in long-term hydrological observatories and other multidisciplinary observatories across the world. Besides monitoring basic climatic and hydrological variables, dedicated experiments are performed in many of these observatories. Hydrological observatories have proven to be crucial for the advance of the hydrological and greater Earth surface and environmental sciences. The accrued benefits include the development of integrated hydrological models that consider complex feedbacks between hydrological compartments. It is of utmost importance to increase awareness and knowledge of these infrastructures to optimize exploration of new hypotheses in hydrology and neighboring and allied disciplines. This special section consists of 23 papers documenting hydrological observatories on four continents covering diverse environmental conditions and research aspects of catchment science. We expect that the use of worldwide long-term hydrological observatories across multiple compartments will help to solve important relevant scientific and societal questions

Correction of Temperature and Electrical Conductivity Effects on Dielectric Permittivity Measurements with ECH(2)O Sensors

The measurement accuracy of low-cost electromagnetic soil water content sensors is often deteriorated by temperature and soil bulk electrical conductivity effects. This study aimed to quantify these effects for the ECH2O EC-5 and 5TE sensors and to derive and test correction functions. In a first experiment, the temperature of eight reference liquids with permittivity ranging from 7 to 42 was varied from 5 to 40 degrees C. Both sensor types showed an underestimation of permittivity for low temperature (5-25 degrees C) and an overestimation for high temperature (25-40 degrees C). Next, NaCl was added to increase the conductivity of the reference liquids (up to similar to 2.5 dS m(-1) for a permittivity of 26-42, up to similar to 1.5 dS m(-1) for a permittivity of 22-26). The permittivity measured with both sensors showed a strong and complicated dependence on electrical conductivity, with both under-and overestimation of permittivity. Using these experimental data, we derived empirical correction functions. The performance of the correction functions for the 5TE sensor was evaluated using coarse sand and silty clay loam soil samples. After correcting for temperature effects, the measured permittivity corresponded well with theoretical predictions from a dielectric mixing model for soil with low electrical conductivity. The conductivity correction function also improved the accuracy of the soil moisture measurements, but only within the validity range of this function. Finally, both temperature and electrical conductivity of the silty clay loam were varied and a sequential application of both correction functions also resulted in permittivity measurements that corresponded well with model predictions