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KevinSpelts

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About KevinSpelts

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  1. In my previous email, I should have used the term "flow direction generator" in place of "flow direction editor" tool under the Arc Hydro GW toolbar. Thank you.
  2. Can you save the results from using the flow direction editor as a shapefile or layer?
  3. GMS 6.x has a feature to allow a simulation to proceed even if MODFLOW does not converge. How does GMS continue the simulation when non-convergence is encoutered at early time steps? Does GMS simply continue the simulation by discarding or modifying simulation data at the moment when non-convergence is first encountered? Thank you. Kevin
  4. Greetings Alan: As an example, in a multi-layer model, streams are located in Layers 2 or 4 (this assumes that overlying layers such as layer 1 are not present or are inactive where the streams are located). Further flooding of some model cells frequently occurred at the top active layer where flooding was not thought to physically occur. To remedy this, the top of layer 1 was set to 10,000 ft above mean sea level (msl). The physical reality indicates that the top of the land surface is about + 4500 ft msl Would GMS use this layer 1 land surface elevation rather than values entered into the STR1 package to derive stream stage or stream conductance? Thank you. Kevin
  5. Is GMS using land surface elevations in a manner that MODFLOW is not aware of? For example, is land surface elevation used by GMS to characterize any aspects of streams or rivers in the STR1 or RIV1 Packages? Thank you.
  6. Is GMS using land surface elevations in a manner that MODFLOW is not aware of? For example, is land surface elevation used by GMS to characterize any aspects of streams or rivers in the STR1 or RIV1 Packages? Thank you.
  7. KevinSpelts

    SFR2

    Greetings: When will SFR2 be added to GMS 6.5? Thank you.
  8. Greetings: I have a question I hope you can help me with. I have two hypothetical models whereby I have a mainstem stream traverse the single layer grid from left to right. 4 separate tributary streams join the mainstem at various and unique locations along the mainstem stream. The main stem and all headwater segments of each of the tributaries have incoming flow. I used GMS 6.0 to execute MODFLOW 2000 and the stream routing STR1 package. If I understand the operation of the STR1 Package correctly, stream routing and stream discharge is sequentially ordered from lower- to higher-numbered segments. Outflow from segment 1 is routed to the next higher numbered segment; this occurs even if these higher numbered segments form portions of separate tributaries. Thus outflow from segment 5 of tributary one will be routed to segment 6 even if segment 6 is the headwater segment of a tributary two; if my understanding is correct, this seems physically unrealistic. I can create two separate models to simulate stream-aquifer interactions of my hypothetical model. (1) GMS allows me to create a simulation with a single coverage containing a main stem stream with 4 tributary streams. The segments that represent the mainstem and tributaries are created from left to right. Thus segment 1 occurs on the left side of the grid whereas segment 30 occurs on the right side of the grid. (2) On the other hand, GMS will allow me to create a simulation with 5 separate coverages; one for the main stem and separate coverages for each tributary. Thus, I created 5 separate coverages in order to keep the outflow from a low numbered segment of a tributary stream from contributing stream flow to a high numbered headwater segment of a separate tributary stream. Other than the method I used to depict streams and stream routing, the models are identical in parametrization (e.g., identical parameters of starting head, hydraulic conductivity, specific yield, and so on). It should be noted that the number of stream segments and incoming flow distribution is different for these two models. I compare the simulation output for each of the models and there is a difference in the rates and volume of stream leakage inputs to and stream leakage outputs from the aquifer between these two simulations (the difference is probably statistically significant for these simulations). If I understand correctly, stream leakage is simply input to the “W” term of the ground water flow equation. My question: Is there a prohibition in MODFLOW from depicting tributary streams using separate coverages? Thank you in advance for your time and attention. Kevin
  9. KevinSpelts

    STR1 Package

    Greetings: In the STR1 Package, "Incoming Flow" can be specified for stream segments that enter into the model as well as head-water segments within the model. However, if incoming flow is not specified by the user, it appears that the default value is "-1": what does the "-1" signify? Thank you. Kevin
  10. Greetings: I have a transient MODFLOW 2000 model in GMS 6.0 whereby my values for recharge (REC) and evapotranspiration (ET) rate and extinction depth vary every thirty days for 4500 days. I enter the REC and ET values and save the project, both with and without executing MODFLOW, to my local disk, a USB drive, and a CD/RW. I close GMS and then reopen the project and check the values for my REC and ET; the REC and ET values stored in the respective REC and ET tables or matrix seem okay for the first 10 or so stress periods but later stress periods have REC and ET that are only vaguely similar to what I first entered (regardless if I have ran MODFLOW or not). Is there some trick in saving time varying REC and ET values? Thank you. Kevin
  11. Greetings: I have a two layer transient model. The model is for an unconfined aquifer and it is nearly flat or horizontal. The model is 1000 m thick and each layer is 500m thick; the top of Layer 1 is 1000 m and the bottom elevation of Layer 1 is 500 m and the bottom elevation of Layer 2 is 0 m. Layer 2 is completely saturated. Layer 1 has a water table at 750 m. Layers 1 and 2 differ in material; Layer 1 is sands and gravels, Layer 2 is primarily gravels. My questions are thus: (1) If I have a tightly cased well that is screened only in Layer 2, should the water surface in the well be at 750 m above the bottom of Layer 2 (or obversely, should the water surface in the well be 250 m below the top layer elevation)? This seems reasonable but I want to be sure that I haven't missed something in ground water hydraulics. (2) Based on the well head information above, should I set the starting head in Layer 1 as 750 m and the starting head in Layer 2 as 500 m (the top elevation of Layer 2)? Or should the starting head be 750 m for both Layers 1 and 2? It seems reasonable that hydraulic head of 750 m should be set the same for both Layers 1 and 2 in this instance, but again, I did not want to miss something unique to MODFLOW 2000. Thank you in advance for your time and attention. Kevin J Spelts
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