Variability and temporal stability of soil water content in a small grassland head water catchment in western Germany observed by a wireless sensor network using time domain transmission sensors
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| Title: | Main Title: Variability and temporal stability of soil water content in a small grassland head water catchment in western Germany observed by a wireless sensor network using time domain transmission sensors |
| Description: | Abstract: The knowledge of variability and temporal stability of soil water content (SWC) is useful for the development of ground truthing strategies of remotely sensed measurements and for hydrolgoical modelling. In this study SWC was determined by a combination of a wireless sensor network (SoilNet) and time domain transmission sensors (TDT). The SoilNet was installed in a grassland headwater catchment in Western Germany within the framework of the TERENO initiative. The nodes of the sensor network were arranged using a 60m grid configuration, with some randomly distributed nodes in between to assess small scale variability. Additionally, meteorological data were obtained from existing weather station at the test site. The TDT sensors were installed at depths of 5, 20 and 50 cm. Soil water content from the TDT sensor response was retrieved using a two-step approach. First, using the Sensor response-permittivity (SRP) model to get the permittivity of the soil, the root mean square error (RMSE) was 1.0171, which was used to express the accuracy of the SRP model. Second, The complex refraction index model (CRIM) was used and fitted to determine the soil water content (SWC) from the permittivity. The experimental results showed that the CRIM model was able to accurately estimate SWC, with RMSE of 0.02822 (5 cm) and 0.02043 (20 and 50 cm). We fitted only the permittivity of the soil particles (2.08 at 5 cm and 3.74 at 20 and 50 cm). A validation of the fitted CRIM models showed that the RMSE were between 0.0133 to 0.0286 cm3·cm-3, which proved that the CRIM model can be applied to the experiment site. The total RMSE from the two-step calibration were 1.0832 for 5cm and 1.0176 for 20 and 50cm. The temperature affection for the SWC is 0.07 Vol.%·°C-1. It revealed to do the temperature corrected SWC in the soil net to get the more accurately data is worthy. Then all the SWC data was corrected in this paper. During the measurement period (20th April to 20th August, 2011) the SWC variability of the top soil was larger than the subsoil (SWC ranged in 5cm from 12.06 to 44.58 Vol.%, from 18.49 to 35.14 Vol.% in 20cm and from 24.86 to 34.65 Vol.% in 50cm). From the rank analyze there are several locations in each depth which are temporal stability. Location 20(MRD=-0.0216±0.1054) and location 18(MRD=-0.0031±0.1284) maybe considered to be the more temporal stable measurement site for 5cm depth. Location 21 (MRD= -0.0064±0.0232) and Location 28 (MRD=-0.0080±0.0336) are more representive for indicating the soil water content at 20cm over time, and location Location 21 (MRD= -0.0064±0.0232) and Location 28 (MRD=-0.0080±0.0336) are more representive for 50cm depth. It was possible to identify sites that were temporally stable and optimal for estimating the area average field SWC. These findings are of relevance for applications of geospatial surface SWC assimilation in hydrologic modeling when only point-scale observations are available, as well as, remotely sensed surface SWC calibration and validation studies. |
Responsible Party
| Creator: | Wie Qu (Author) |
| Publisher: | CRC/TR32 Database (TR32DB) |
| Publication Year: | 2013 |
Topic
| TR32 Topic: | Soil |
| Related Subproject: | C1 |
| Subject: | Keyword: PhD Report |
File Details
| Filename: | Report2_Qu_2011.pdf |
| Data Type: | Text - Text |
| File Size: | 741 KB |
| Date: | Available: 01.10.2011 |
| Mime Type: | application/pdf |
| Data Format: | |
| Language: | English |
| Status: | Completed |
Constraints
| Download Permission: | Only Project Members |
| General Access and Use Conditions: | According to the TR32DB data policy agreement. |
| Access Limitations: | According to the TR32DB data policy agreement. |
| Licence: | [TR32DB] Data policy agreement |
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Specific Information - Report
| Report Date: | 1st of October, 2011 |
| Report Type: | PhD Report |
| Report City: | Jülich, Germany |
| Report Institution: | Institute of Bio and Geosciences Agrosphere (IBG-3), Research Center Jülich |
| Number of Pages: | 19 (1 - 19) |
| Further Information: | TR 32 Student Report Phase II |
Metadata Details
| Metadata Creator: | Wei Qu |
| Metadata Created: | 04.12.2013 |
| Metadata Last Updated: | 04.12.2013 |
| Subproject: | C1 |
| Funding Phase: | 2 |
| Metadata Language: | English |
| Metadata Version: | V50 |
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| Page Visits: | 776 |
| Metadata Downloads: | 0 |
| Dataset Downloads: | 1 |
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