Exercise 1

The figure below shows stream temperatures measured at three different times of day (3:00, 10:00 and 15:00 hours) by an optical fiber placed at the bottom of the Walker River in western Nevada, USA, during low flow. The flow in the stream at the upstream end (0.0 meters) was measured as 0.4 m³/s (~14.1 ft³/s). Using this information:

1. Estimate the location of a groundwater inflow.
2. Estimate the temperature of the underlying groundwater using the approach of Selker and others (2006).
3. Calculate the volumetric flux (in m³/s) of groundwater entering the stream at 3:00 and 15:00 hours.
4. Assuming the DTS can resolve differences in temperature in space accurately to 0.1 °C, what is the minimum rate of groundwater inflow that could be observed in this river given that the flow in a river is: a) 1 m³/s; and, b) 10 m³/s, the stream temperature is 15 °C and the groundwater differs from the stream temperature by 5 °C.

Temperatures at different times of day at Walker River, Nevada, USA.

Click for solution to Exercise 1