For a project I'm working on, a subbasin 1A flows to a depression which then overflows to an existing culvert. I am unsure what is the correct way to model this. I tried both these ways:
Method 1. I modeled the depressional area as a reservoir with a spillway outlet. I had to add an arbitrary orifice outlet at the bottom of the depression with diameter 0.001 to effectively produce 0 CSS discharge under the overflow elevation.
Method 2. I divided the depressional storage by the drainage area and included it as an initial abstraction over the entire subbasin 1A under the Simple Surface input. I made a separate reservoir with the spillway set at the depression overflow elevation to model discharge flows.
However, I get different discharges for both methods. Method 1 results in an increased discharge over method 2.
Method 1. I modeled the depressional area as a reservoir with a spillway outlet. I had to add an arbitrary orifice outlet at the bottom of the depression with diameter 0.001 to effectively produce 0 CSS discharge under the overflow elevation.
Method 2. I divided the depressional storage by the drainage area and included it as an initial abstraction over the entire subbasin 1A under the Simple Surface input. I made a separate reservoir with the spillway set at the depression overflow elevation to model discharge flows.
However, I get different discharges for both methods. Method 1 results in an increased discharge over method 2.