Topic: Eel - Inflow Van Arsdale versus Rel Lake Pillsbury
|Posted: Jun 12, 2007Post Subject: Eel - Inflow Van Arsdale versus Rel Lake Pillsbury
|Dreamflows started reporting computed inflow to Van Arsdale reservoir on the Eel today. This gauges serves the Pillsbury run. Only daily average flow information is available, so look on the daily report (not the realtime). Currently the two flows on the report 'Eel - Rel Lake Pillsbury' and 'Eel - Inflow Van Arsdale' are very similar, but they may diverge significantly in winter. Rel Lake Pillsbury is upstream of the Pillsbury run, while Inflow Van Arsdale is downstream, so the flow on the Pillsbury run should be somewhere in between.|
You will soon notice however that the reported inflow to Van Arsdale is often less than the release from Lake Pillsbury, even though Van Arsdale is lower down and therefore the flow should be higher. The simple explanation is that Van Arsdale inflow is computed from reservoir information, which is error prone. Sometimes it'll be more than Lake Pillsbury, sometimes less. A fuller explanation would include the fact that all river gauges are inaccurate to some extent, which will compound the problem. An even fuller explanation includes the fact that Van Arsdale is many miles downstream of Pillsbury, so we need to take flow travel time into account when comparing the two gauges (but daily averages don't do that). Happily, the errors should be minor, and averaging out the two flows should give you a reasonable approximation of the actual flow on the Pillsbury run.