Dear Sir or Madam,
I have posted before the question regarding groundwater modelling in my profile, yet it seems that I have not fully understood the concept nor did my supervisor fully agreed to what I presented to him for the results of my groundwater model in the previous question. Now I would like to ask whether the boundary conditions are correctly defined from my perspective, if not, I would like to ask your review and therefore correction if possible. I am using software QGIS and Processing Modflow version 5 (both are freeware) to compile and model the groundwater flow. Attached are the pictures to my work so far. The real problem is to actually find out whether there would be influence from the well located in the right side (4) to the three wells on the left of that well (1,2,3).
Hello Adi,
Firstly, it is not realistic to have no-flow boundaries that become constant-head boundaries on the same section (like on the South and West sections of your model).
I would extent your region so that most of the boundaries would be no-flow conditions (corresponding to GW divides) and I would affect a constant-head boundary only at the discharge point of the waterways draining your region of interest. This way, your model would correspond to a watershed which has more sense than an almost arbitrary design of the boundaries of your model.
Secondy, in the waterways that are inside your watershed region, I would apply Cauchy conditions along these waterways. Finally, for recharge, you should apply a flow condition at the surface of your model as well as you should apply flow conditions in your pumping wells.
I attach in my reply an article which could possibly help you to design your model based on a similar case.
Hope this help and good luck
generally watershed boundaries that contained of the study area, can assume as the model domain. So, the model domain can assume as no-flow boundary and outlet/inlet rivers as specified-head boundaries. However the physical boundaries like impermeable fault or river, are preferred.
Hello Sr. Adi,
For better understanding in the conceptualization of the system, keep these guidelines in mind:
System and Boundary Conceptualization in Ground-Water Flow Simulation
https://pubs.usgs.gov/twri/twri-3_B8/
Guidelines for Evaluating Ground-Water Flow Models
https://pubs.usgs.gov/sir/2004/5038/
Analytically, boundary conditions in groundwater modelling are required mathematical conditions/imposed contentions that must be met in order for the solution to a set of differential equations involving groundwater modeling to be found. However, the numerical approach, which invokes software programs used here is an approximation to the analytical case. However, the BC for no flow, which covers large part of the study area is doubtful as this is supposed to be guided by geology. Besides, the condition warranting the choice of constant head does not consider the source - sink orientation of the flow. However, where there seems to be a tube of flow is chosen to be the constant head. The contour lines do not seem to mean anything to the researcher and this makes his result indeterminate. The role of already known geology is very important here in order to help you parametrize the impervious and pervious zones. This will also enable you to constraint your result with geology as well as making you to have fidelity in your result
limit your model domain to watershed borders and rivers. so the watershed borders can defined as no-flow boundaries and rivers can defined using river package of Modflow code (or general head boundary in other codes) in a model.