PhD research: Monitoring temporary streams in mountainous headwater catchments
Temporary streams are unique ecosystems. They are common and are estimated to account for more than half of the world’s total river network length and discharge. Temporary streams alternate between wet and dry states, causing expansion and contraction, connection and disconnection of the flowing stream network. These changes in the flowing stream network can have a significant influence on perennial stream water quality and quantity. However, temporary streams are largely unmonitored and understudied, especially in headwater catchments. Conventional methods to study streamflow are often not suitable for monitoring temporary streams because of the high spatial variability, the complexity of setting up streamflow gauging stations and high sediment transport in temporary streams and high costs associated with each measurement. We have therefore designed a low cost system to monitor temporary stream dynamics in mountainous headwater catchments. The newly developed system consist of consists of an Arduino microcontroller, a data logger and 4 sensors (electro resistivity, water level switch, temperature and flow). The high spatial and temporal resolution of the data from this system provides important information on the flowing stream network pattern and the influence of stream network connection on perennial stream water quality.
Our study takes place in one of the headwater catchments of the Studibach (Watershed 41, 0.12 km²) in the Alptal during the summer-fall snow-free season. The monitoring setup consists of a network of 30 of the newly developed low cost sensor units. The sensors provide high temporal resolution on the presence of water and the occurrence of flow in the channel. The data from the sensors was compared with the time lapse camera pictures taken in 2016 to determine the performance of the system in recording the timing of channel state changes (water/no water and flow/no flow). The results show that the sensors performed well. However some adjustments were made for 2017 to make the sensors even more robust and low-maintenance and to ensure high quality data over a long monitoring period. These new sensors recorded data on the presence of water and flow in the temporary streams in the Alptal during the late summer-fall 2017 and will be installed in tributaries of the Reppisch in winter 2018.
The sensor data will be used to map the expansion and contraction of the flowing stream network during rainfall events. We will analyse the changes in the flowing stream network to determine how the characteristics of the monitoring sites (topographic indices, land cover and streambed characteristics) and wetness conditions (rainfall amount/intensity, groundwater levels, soil moisture, streamflow at the outlet) affect the occurrence of streamflow.
Furthermore, the sensor unit data will be compared to water quality data from the perennial and temporary stream reaches during several rainfall events. This data will be used to analyze the influence of stream network expansion and connection on perennial stream water quality.
Temporary streams, stream network patterns, monitoring, low cost sensor network, pre-alpine headwaters, connectivity, stream water quality
Dr. Ilja van Meerveld (firstname.lastname@example.org)
Prof. Dr. Jan Seibert (email@example.com)