mLM fork: Provision for lakes that outflows directly to another lake
Background
- There would be cases in which a reservoir lake extent would extend upstream such that it reaches the outflow L0 of upstream reservoir lake.
- Or there could be natural lakes where the lake downstream has extent up to the waterfall L0 cell of the upstream lake.
Issue
- The code at the moment only checks nodes for being outlets and not lakes as in aforementioned cases.
- Conversely, it could be that the reservoirs are close to each other but not connected. However, if user gives high values for dam crest level of downstream reservoir, this condition can (erroneously) arise.
- I came across such case in Khuzestan where the lake of Masjed e-Soleyman (downstream) extended up to the outflow L0 cell of Shahid Abbaspour reservoir (upstream) with high dam crest level.
Solution
- There needs to be a provision where lakes are checked for being lake outlets of upstream lakes.
- If such cases arise, which would be very rare, the user is informed at runtime with lake indices of the upstream-downstream lakes
- User is also provided with the hint that lowering dam crest level of the downstream dam may solve the issue, in case the lake connection is erroneous.
- Lowering of the dam crest level for Masjed e-Soleyman (downstream reservoir) helped to avoid this situation as follows -