Model V12s


A problem with the RRCA Model Version 12p7 of July 1, 2003 was reported by Nebraska on August 4, 2003 as follows:

Chuck Spalding has reported a bug in the representation of streams in the model. It affects the model for those stress periods after reservoirs go on line. At each of the reservoir locations, cells within the reservoir reaches that are upstream of the reservoir pool are omitted. In most cases these amount to 1 or 2 cells, however, in the case of Harry Strunk Reservoir 12 cells are omitted representing a length of 7 or 8 miles. Please take a look at the MODFLOW STREAM Package 12.str. A PDF is attached showing 2 figures. The first figure is the stream package under steady-state conditions and the second figure is the stream package in December 2000, representing post-reservoir conditions.

The aforementioned PDF file shows the streams before and after the reservoirs as reproduced here:


The same information can be displayed in an alternative format as shown here with a light blue color used to represent stream cells that are active before and after the reservoirs come on line, red cells represent stream cells that are active only before the reservoirs come on line, and yellow cells represent stream cells that are active only after the reservoirs come on line.

The same information is displayed in the image below zoomed in on Harry Strunk reservoir on the right and Hugh Butler on the left.

Note that in both cases there are cells that appear only before or only after the reservoirs come on line. The reason why this occurs is best illustrated by the schematic diagram of the middle portion of the stream network shown below.

The stream network was adopted from the original USGS work by Landon et. al. The system topology, and in particular the Segment and Reach numbering was adopted verbatim. On Red Willow creek, for example, the sequence Segment 60, Segment 132, Segment 159, Segment 160 was adopted, with Segment 132 representing Hugh Butler Reservoir. The topology of Medicine Creek is more complex as can be seen above. It is, however, of interest to note that Segment 170 represents Medicine Creek above Harry Strunk, Segment 183 represents Harry Strunk Reservoir, and Segment 184 represents Medicine Creek below Harry Strunk Reservoir. The division between Segments 170 and 183 occurs at the Medicine Creek Above Harry Strunk gage.

In order to simplify the post-processing, streams and reservoirs are represented using the MODFLOW STREAM package. This permits the impacts to be captured by a small number of accounting points in the HYDMOD package which can then be post-processed for accounting purposes. Unfortunately, there is a limitation in the HYDMOD package that requires the number of segments and reaches per segment to remain the same throughout the simulation. This creates a particular problem in the case of the reservoirs. Reservoirs are simulated as they were built. Therefore, prior to a reservoir coming on line, the stream is simulated crossing the reservoir. When the reservoir starts to store water, the reservoir stage is set based on historical stage measurements, while the reservoir area is represented using a number of cells. A different number of cells is typically required to simulate the pre-reservoir stream and the reservoir. In order to accommodate the HYDMOD package limitation, padding stream reaches were used. In the padding reaches, the stream-aquifer conductance term was set to zero. This allows water in the stream to be routed through these stream reaches, but have no interaction with the groundwater system.

Reservoirs were simulated by setting an inflow into the segment containing the reservoir of 1,000,000 cfs. This flow rate was chosen to readily distinguish reservoir segments from stream segments, and to allow for any amount of reservoir leakage that could reasonably occur. The reservoir leakage is then calculated by subtracting 1,000,000 from the stream flow at the end of the reservoir segment. Note, however, that since stream flows can only be specified at the beginning of a segment, this requires reservoirs to occupy an entire segment.

In the case of Harry Strunk reservoir, Segment 183 is used to represent the reservoir. However, as noted in the Nebraska email, Segment 183 actually starts at the Medicine Creek Above Harry Strunk gage which is several miles above the reservoir proper. Since the reservoir cells were selected to only cover the reservoir proper, there is a resulting gap in the Medicine Creek stream cells between the gage and the reservoir.

Description of the Solution

The source of the problem is that Segment 183 goes from the Medicine Creek above Harry Strunk gage to the Harry Strunk Dam. The obvious solution is therefore to break Segment 183 into two segments: One segment that goes from the gage to the inflow into the reservoir, and a second segment that covers the reservoir. In order to avoid renumbering the system, the first 12 reaches in Segment 183 are appended to Segment 170, while the remaining reaches in Segment 183 are renumbered from one and becomes the new Segment 183.

The accounting calculations for Medicine Creek adds the impacts calculated above Harry Strunk reservoir to the impacts at the confluence with the main stem. The above Harry Strunk reservoir accounting point was Segment 170 Reach 5 which was the last reach above the reservoir represented. However, since Segment 170 new is extended by 12 reaches, a new accounting point is needed at Segment 170 Reach 17. This accounting point was named AcctHarryStrunk.

A new simulation was generated to evaluate the impacts of the above changes. The simulation was named V12s using the previously established naming scheme.

The program fixstr was written to modify the input file to mkstr as well as produce new HYDMOD and accounting package input files. The fixstr program takes the 11.str.0 input file used to define the pre-reservoir stream network and produces 12.str.0. The difference between 11.str.0 and 12.str.0 is that the first 12 reaches of Segment 183 are appended to Segment 170 as described above. The mkstr program is then modified to read 12.str.0 instead of 11.str.0, and to produce 12s.str instead of 12.str. Furthermore, the fixstr program creates 12s.hyd from 12.hyd by adding the AcctHarryStrunk location and modifying the HarryStrunk location from Segment 183 Reach 19 to Segment 183 Reach 8 to account for the fact that Harry Strunk Dam is now at a renumbered reach. Finally, the fixstr program modifies the accounting parameter file acct.par to produce acct.12s which replaces SI1700056841000 with SI170017AcctHarryStrunk.

The MODFLOW V12s simulations was then be repeated with the V12p7 input files except that 12.str is replaced by 12s.str and 12.hyd is replaced by 12s.hyd. Output files and input files that were changed are provided.

Results

The predicted stream flows for V12s are virtually identical to that for V12p7. This is to be expected since the flow into Harry Strunk reservoir is not routed to any other segment. In the following figures, the red line representing V12s paints over the blue line representing V12p7.
01 Landsman Creek Near Hale, CO
02 North Fork Republican River at CO-NE Stateline
03 North Fork Republican River Near Wray, CO
04 South Fork Republican River Near CO-KS State Line
05 South Fork Republican River Near Idalia, CO
06 Beaver Creek at Cedar Bluffs, KS
07 Beaver Creek at Ludell, KS
08 Beaver Creek near Herndon, KS
09 Prairie Dog Creek above Keith Sebelius Lake, KS
10 Prairie Dog Creek at Norton, KS
11 Prairie Dog Creek near Woodruff, KS
12 Sappa Creek near Lyle, KS
13 Sappa Creek near Oberlin, KS
14 South Fork Sappa Creek Near Achilles, KS
16 Arikaree River at Haigler, NE
17 Beaver Creek near Beaver City, NE
18 Blackwood Creek near Culbertson, NE
19 Brushy Creek near Maywood, NE
20 Buffalo C nr Haigler, NE
21 Center Creek at Franklin, NE
22 Cottonwood Creek near Bloomington, NE
23 Driftwood Creek near McCook, NE
24 Elm Creek at Amboy, NE
25 Fox Creek at Curtis, NE
26 Frenchman Creek - Gain-Loss Enders to Palisade, NE
27 Frenchman Creek - Gain-Loss Palisade to Culbertson, NE
28 Frenchman Creek at Culbertson, NE
29 Frenchman Creek near (above) Champion, NE
30 Frenchman Creek near Hamlet, NE
31 Frenchman Creek near Imperial, NE
32 Medicine Creek above Harry Strunk Lake, NE
33 Medicine Creek at Maywood, NE
35 Muddy Creek at Arapahoe, NE
36 Red Willow Creek - Gain-Loss Below Hugh Butler to Red Willow, NE
37 Red Willow Creek above Hugh Butler Lake, NE
38 Republican - Gain-Loss Below Harlan to Guide Rock, NE.
39 Republican - Gain-Loss Below Swanson Reservoir to McCook, NE
40 Republican - Gain-Loss Benkleman to Swanson, NE
41 Republican - Gain-Loss Cambridge to Orleans, NE
42 Republican - Gain-Loss Guide Rock to Hardy, NE
43 Republican - Gain-Loss McCook to Cambridge, NE
44 Republican River at (nr) Culbertson, NE
45 Republican River at Benkelman, NE
46 Republican River at Max, NE
47 Republican River near Bloomington, NE
48 Republican River near Hardy, NE
49 Rock Creek at Parks, NE
50 Sappa Creek near Beaver City, NE
51 Sappa Creek near Stamford, NE
52 South Fork Republican River near Benkelman, NE
53 Stinking Water Creek near Palisade, NE
54 Stinking Water Creek near Wauneta, NE
55 Thompson Creek at Riverton, NE
56 Turkey Creek at Edison, NE
57 Turkey Creek at Naponee, NE
Hugh Butler Reservoir Leakage
Bonny Reservoir Leakage
Keith Sebelius Reservoir Leakage
Enders Reservoir Leakage
Harlan County Reservoir Leakage
Harry Strunk Reservoir Leakage
Swanson Reservoir Leakage
Confluence: North Fork Republican
Confluence: Arikaree
Confluence: Buffalo
Confluence: Rock
Confluence: South Fork Republican
Confluence: Frenchman
Confluence: Driftwood
Confluence: Red Willow
Confluence: Medicine
Confluence: Beaver
Confluence: Sappa
Confluence: Prairie Dog Pre
Confluence: Prairie Dog Post

There are some changes in the heads in the immediate vicinity of the twelve stream reaches that are appended to Segment 170. The differences between the heads predicted by V12p7 and V12s are shown for the steady state, 12/31/1940, 12/31/1970 and 12/31/2000. The head differences are the result of the heads being pulled up between V12p7 and V12s when the stream is loosing, and the heads being pulled down when the stream is gaining. Prior to September 1949 when the reservoir comes on line, there is, of course, no difference between V12p7 and V12s. At the end of the simulation, the maximum increase in head from V12p7 to V12s is 14.5 feet, and the maximum decline in head is 25.1 feet. In 8 cells the decline exceeded 10 feet, in 66 cells the decline exceeded 1 foot and in 197 cells the decline exceeded 0.1 feet. In 1 cell, the increase exceeded 10 feet, In 6 cells, the increase exceeded 1 foot, and 10 cells the increase exceeded 0.1 feet. Therefore, a head change of greater than 10 feet was observed in 9 cells, a change of 1 foot was observed in 72 cells and a change of greater than 0.1 feet was observed in 207 cells. The maximum distance a 0.1 foot head change was observed from Medicine creek was approximately 10 miles.

Impacts

Impacts were calculated using the acct program, but using the acct.12s parameter file instead of the acct.par file. The results for V12p7 and 12s are shown below, calculated for 1981-2000 as before:

V12p7
V12s

As is to be expected, the predicted impacts for Colorado and Kansas remain unchanged between V12p7 and V12s. The impacts for Nebraska remain unchanged except on Medicine Creek and Harry Strunk reservoir as summarized below:

1981-2000 Average Annual Impact (acre-feet)
ItemMedicine
Creek
Harry
Strunk
Reservoir
Nebraska
Total
Nebraska Pumping V12p7 11999 360165073
Nebraska Pumping V12s 13151 195166060
Nebraska Pumping Change +1152 -165 +987
 
Nebraska Mound V12p7 7998 0 16328
Nebraska Mound V12s 7976 0 16310
Nebraska Mound Change -22 0 -18
 
Nebraska Impact Net Change+1174 -165 +1005



Problem Description (PDF)
Stream Cells without Reservoirs
Stream Cells with Reservoirs
Stream Cell Differences (Global)
Stream Cell Differences (Detail)
Stream Network Schematic
Data Files
01 Landsman Creek Near Hale, CO
02 North Fork Republican River at CO-NE Stateline
03 North Fork Republican River Near Wray, CO
04 South Fork Republican River Near CO-KS State Line
05 South Fork Republican River Near Idalia, CO
06 Beaver Creek at Cedar Bluffs, KS
07 Beaver Creek at Ludell, KS
08 Beaver Creek near Herndon, KS
09 Prairie Dog Creek above Keith Selbelius Lake, KS
10 Prairie Dog Creek at Norton, KS
11 Prairie Dog Creek near Woodruff, KS
12 Sappa Creek near Lyle, KS
13 Sappa Creek near Oberlin, KS
14 South Fork Sappa Creek Near Achilles, KS
16 Arikaree River at Haigler, NE
17 Beaver Creek near Beaver City, NE
18 Blackwood Creek near Culbertson, NE
19 Brushy Creek near Maywood, NE
20 Buffalo C nr Haigler, NE
21 Center Creek at Franklin, NE
22 Cottonwood Creek near Bloomington, NE
23 Driftwood Creek near McCook, NE
24 Elm Creek at Amboy, NE
25 Fox Creek at Curtis, NE
26 Frenchman Creek - Gain-Loss Enders to Palisade, NE
27 Frenchman Creek - Gain-Loss Palisade to Culbertson, NE
28 Frenchman Creek at Culbertson, NE
29 Frenchman Creek near (above) Champion, NE
30 Frenchman Creek near Hamlet, NE
31 Frenchman Creek near Imperial, NE
32 Medicine Creek above Harry Strunk Lake, NE
33 Medicine Creek at Maywood, NE
35 Muddy Creek at Arapahoe, NE
36 Red Willow Creek - Gain-Loss Below Hugh Butler to Red Willow, NE
37 Red Willow Creek above Hugh Butler Lake, NE
38 Republican - Gain-Loss Below Harlan to Guide Rock, NE.
39 Republican - Gain-Loss Below Swanson Reservoir to McCook, NE
40 Republican - Gain-Loss Benkleman to Swanson, NE
41 Republican - Gain-Loss Cambridge to Orleans, NE
42 Republican - Gain-Loss Guide Rock to Hardy, NE
43 Republican - Gain-Loss McCook to Cambridge, NE
44 Republican River at (nr) Culbertson, NE
45 Republican River at Benkelman, NE
46 Republican River at Max, NE
47 Republican River near Bloomington, NE
48 Republican River near Hardy, NE
49 Rock Creek at Parks, NE
50 Sappa Creek near Beaver City, NE
51 Sappa Creek near Stamford, NE
52 South Fork Republican River near Benkelman, NE
53 Stinking Water Creek near Palisade, NE
54 Stinking Water Creek near Wauneta, NE
55 Thompson Creek at Riverton, NE
56 Turkey Creek at Edison, NE
57 Turkey Creek at Naponee, NE
Hugh Butler Reservoir Leakage
Bonny Reservoir Leakage
Keith Sebelius Reservoir Leakage
Enders Reservoir Leakage
Harlan County Reservoir Leakage
Harry Strunk Reservoir Leakage
Swanson Reservoir Leakage
Confluence: North Fork Republican
Confluence: Arikaree
Confluence: Buffalo
Confluence: Rock
Confluence: South Fork Republican
Confluence: Frenchman
Confluence: Driftwood
Confluence: Red Willow
Confluence: Medicine
Confluence: Beaver
Confluence: Sappa
Confluence: Prairie Dog Pre
Confluence: Prairie Dog Post
Head Difference: Steady State
Head Difference: 12/31/1940
Head Difference: 12/31/1970
Head Difference: 12/31/2000
Impacts V12p7
Impacts V12s
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