Hello everyone： I now need to simulate the water quality of a river.I have daily flow data from the upper reaches of the river.Water level data downstream of rivers.But I don’t have flow data downstream of the river.So can I use the open boundary condition and set the downstream water level as Time Series Pressure.(the 1.jpg is measured data）
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That could work. The thing you need to be aware of is that Open Boundaries are infinite sources and sinks of water. This means that if at any point your downstream water levels are even slightly higher than the water levels upstream, this will allow water to come back into the system which might not be appropriate for your system.Another option is to develop a rating curve for the downstream boundary which would use the upstream elevation to determine how much flow to let out of the system. This would be an iterative process though since you don’t have measured discharges at your downstream station.
Hi Tom， I have 2 questions: (1) why "if at any point your downstream water levels are even slightly higher than the water levels upstream, this will allow water to come back into the system "? I mean, when the model has a flow boundary upstream and a water level boundary downstream, will “downstream water levels are even slightly higher than the water levels upstream” happen in calculating? Because you konw, when we set the initial condition, the initial water level is lower in the downstream.(2) Is there any example about “develop a rating curve for the downstream boundary”? I am interested in that.
Thanks @Tom. I have the same question with “in art”, can you give a case or a little more detail on how to establish “rating curve for the downstream boundary”.
The short answer to your original question is, yes. The open flow boundary looks like it would be your best option based on the plot you provided. Sorry to cause confusion.In the statement that In Art is referring to in (1), I was mainly talking about something that usually occurs in tidally influenced rivers. If that is not something that occurs in your system then you should not worry about it.I’m sorry I did not look at your plots when I initially responded. Your system is clearly not tidally influenced and appears to be managed to some extent (perhaps a reservoir?). Also, I assume the flow boundary at the upstream end is at a higher elevation and will not be affected by the large spike in water levels in late July you showed in your plots. Any large, sudden changes in water levels at an open boundary will likely cause instabilities in your model and could cause it to crash.Regarding iterative processes to create a rating curve for the downstream boundary, it depends on what data is available for the system:1) If you have any period of time, even outside of your period of study where you could compare water surface elevation and discharge across a reasonable range of flow conditions.2) If there is some other gage on the river with paired discharge and water surface elevation you could try shifting the elevations on the rating curve from that station. If there are other major inflows to the river within the boundaries of your model this will probably not work.I don’t think I can provide you any more guidance than that since it is not a feature of EFDC_Explorer.
Thanks again！ In order to have a water landscape in winter, there are gate controls upstream and downstream of the river.At the same time, the flow rate of this river is very small.So I think this river can be understood as a small reservoir.