Draft Imnaha Subbasin Summary November 30, 2001 Prepared for the Northwest Power Planning Council Subbasin Team Leader



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Hydrology

Water Quantity

The Imnaha River subbasin drains an area of 980 square miles. The Imnaha mainstem extends approximately 63.5 miles upstream from its confluence with the Snake River to the North and South Forks in the Eagle Cap Wilderness (Wallowa Whittman National Forest 1994). Primary tributaries, starting at the confluence with the Snake River, include Cow Creek, Lightning Creek, Horse Creek, Big Sheep Creek, Freezeout Creek, Grouse Creek, Summit Creek, Crazyman Creek, Gumboot Creek, Dry Creek, Skookum Creek, South Fork, Middle Fork, and North Fork Imnaha River.

Current flow data in the Imnaha has been collected from the USGS-maintained gage located near the town of Imnaha (gage #13292000) since 1928 (Table 3). The discharge measured at the gaging station represents 622 square miles, 72% of the entire subbasin (Wallowa Whitman National Forest 1994). Three other gages, two of which collected only peak flow data, were historically used in the subbasin, yet are no longer in service. These include the Mahogany Creek station (gage #13291200), the Gumboot station (gage #13291000) and the Deer Creek station (gage # 13291400) (Table 3).

The river’s annual mean discharge at the Imnaha gaging station is 517 cfs, based on 73 years of flow data (Figure 7). The highest mean annual discharge (12,500 cfs) occurred during 1996, compared to the lowest mean annual discharge of 184 cfs, which occurred during the 1977 drought year (US Geological Survey, Water Quality Report 1999). Monthly flow statistics are shown in Table 4.

Table 3. USGS gaging summary, Imnaha River Basin, Oregon

Gage No.


Gage Name

Latitude

Longitude

Area (mi2)

Elevation (ft)

Period of Record

113291400

Deer Cr nr Imnaha

45:33:00

116:47:30

2

3760

65,71-72,74-76,78-79


113291200

Mahogany Cr nr Homestead

45:12:15

116:52:05

4

3740

65-72,75

13291000

Imnaha above Gumboot Cr

45:11:00

116:52:00

100


3813

45-53

13292000


Imnaha at Imnaha

45:33:45

116:50:00

622

1941

29-98

1/ Peak flows only

Table 4. Average monthly flows in the Imnaha River at the town of Imnaha (1928-2000)



Flow

(cfs)

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sept

Mean


157

185

200

213

330

417

942

1575

1336

569

198

146

Flood frequency analysis, based on 73 years of data from the Imnaha gage is shown in Table 5. The Imnaha River reached a record high discharge of 20,200 cfs during a rain-on-snow flood event on January 1, 1997 (U. S. Geological Survey). The event triggered landslides, destroyed a house (Tom Smith, NRCS Soils Scientist, personal communication February 8, 2001), and significantly modified stream channel morphology, specifically mainstem tributaries, through mass movements of bedload material (USDA Forest Service 1998). The record low was 25 cfs on November 22-23 in 1931. Flow duration curves, as they relate to important salmonid life stages, are presented in Appendix B.


Table 5. Annual flood flow frequency summary for two gauges in the Imnaha subbasin.

Exceedance Probability (%)

Return Period (yrs)

Gage #13292000


0.99

1

974

0.50

2

2,607

0.20

5

4,284

0.10

10

5,739

0.05

20

7,435

0.02

50

10,145

0.01

100

12,625


Figure 7. Average annual flows in the Imnaha subbasin (Imnaha gage #13292000) (USGS data)


Diversions, Impoundments, and Irrigation Projects

The Imnaha subbasin has one large diversion and various smaller irrigation projects. There are no known water storage structures large enough to require inspection by the county water master because of their potential threat to people or property (S. Hattan, OWRD, personal communication February 2, 2001).

Water diversions were built in the subbasin starting in the early 1900s (Wallowa County and Nez Perce Tribe 1993). Early diversions enabled people to irrigate and more successfully farm land along streams and in the subbasin’s valleys (Wallowa County and Nez Perce Tribe 1993). Big Sheep Creek, Little Sheep Creek, Imnaha River, and their tributaries all had water diverted from them for agriculture (Wallowa County and Nez Perce Tribe 1993). Many of the smaller water diversion projects in the subbasin were abandoned during the World War II era, as people left to join the war effort and industrialized agriculture replaced the reliance on canal systems (Wallowa County and Nez Perce Tribe 1993). Current water withdrawals are used primarily for livestock and irrigation and are regulated by the county water master (Wallowa-Whitman National Forest 1998).

The Wallowa Valley Improvement Canal is the only major irrigation diversion in the subbasin (Nez Perce Tribe et al. 1990). The project was started in the early 1900s. By the time the project was completed, a canal was built from Big Sheep Creek in the Imnaha subbasin to Prairie Creek in the Wallowa Valley (Wallowa County and Nez Perce Tribe 1993). Downstream of the Big Sheep Creek forks, water is diverted from Big Sheep Creek and sent via a canal to Little Sheep Creek (Nez Perce Tribe et al. 1990). A diversion dam in Little Sheep Creek leads to a second canal that transports the water to the Wallowa Valley where it is used for irrigation (Nez Perce Tribe et al. 1990). Along the course of the canal, water from Big Sheep Creek, Salt Creek, Little Sheep Creek, Redmont Creek, Cabin Creek, Canal Creek and Ferguson Creek is diverted (USDA Forest Service 2000a). Most of the canal supports populations of resident bull and rainbow trout.

In 1983, three small hydroelectric production facilities, Upper Little Sheep Creek, Canal Creek, and Ferguson Ridge were constructed along the Wallowa Valley Improvement Canal in the Sheep Creek subwatershed (USDA Forest Service 2000a; Mason et al. 1993). A separate canal, known locally as the “Power Canal”, was constructed above the Wallowa Valley Improvement Canal in an effort to obtain the necessary head required for electricity generation. Dropping diverted water rapidly through a penstock to the powerhouse, and then returning flows to the canal generated electricity. The facilities and canal, which were operated and maintained by Joseph Hydro Associates, were eventually removed in 1997 (USDA Forest Service 2000a). During its removal, approximately three miles of ditch was de-watered, necessitating a bull trout salvage operation by the USFS and ODFW during which an estimated 600 fish were saved (USDA Forest Service 2000a).



Water Rights

In 1877, a decree was filed for 23.16 cfs of water to be diverted from McCully Creek between April 1 – July 31 for irrigation, plus an undefined amount for stock and domestic use, which was estimated to be about 0.09 cfs (Bliss 2001). As shown in Table 6, additional rights were filed over the years for the annual diversion of McCully Creek waters into the Wallowa subbasin for use during different times of the year. The decree of 1905 is considered to be the first water right filed associated with the Wallowa Valley Improvement Canal, which at the time was called Sheep Creek Ditch, granting an undefined contribution of as much as 162.74 cfs from McCully Creek, Little Sheep Creek, and all tributaries crossed by the ditch up to but not including Big Sheep Creek during the months April – July (Bliss 2001; NPT et al. 1990). A subsequent filing for 33.65 cfs from Big Sheep Creek and again all springs or tributaries along the canal (not including Little Sheep Creek or McCully Creek) was added to the system in 1919 (Nez Perce Tribe et al. 1990).. Permits were granted in following years that provided for a total right of 114.57 cfs (based on 1877, 1941 & 1976 rights) of water to be diverted from McCully Creek each year during April 1 – July 31 for irrigation. Similarly, annual irrigation rights for 57.79 cfs (based on 1877, 1941 & 1976 rights) of McCully Creek water were granted for use during August 1 – October 15. Between 0.85 cfs and 2.55 cfs of water is used for stock and domestic use during October 16 – March 31, with about 0.18 – 0.27 cfs assigned to McCully Creek diversion #2 (Table 6) (Bliss 2001). The net result of water rights appropriated on McCully Creek is that all water from the creek is diverted all year.

Table 6. Summary of rights to divert McCully Creek waters into the Wallowa subbasin (Bliss 2001)



Diversion Rights

April 1 – July 31



Diversion Rights

August 1 – October 15



Diversion Rights

October 16 – March 31



Decree (1877 rights1/):

23.16 cfs primary rights from McCully Creek for irrigation, plus an undefined amount for stock and domestic use estimated to be about 0.09 cfs



Decree (1877 rights):

11.58 cfs from McCully Creek for irrigation, plus an undefined amount for stock and domestic use estimated to be about 0.09 cfs



Decree (1877 rights):

An undefined amount for stock and domestic use estimated to be about 0.09 cfs plus an undefined flow needed to keep ditches from freezing during the winter. Out of stream domestic use is estimate to be negligible during non-irrigation season. Total use is estimated to be less than 0.18 to 0.27 cfs, 2 to 3 times the estimated minimum.



Decree (19052/ & 19192/ rights):

Undefined McCully Creek contribution to 162.74 cfs primary rights diverted into Sheep Creek Ditch, including undefined part of 129.09 cfs for stock and domestic use estimated to be about 0.76 cfs. Supplemental 1919 right does not include McCully Creek.


Decree (1905 & 1919 rights):

Undefined McCully Creek contribution to 81.35 cfs diverted into Sheep Creek Ditch, including undefined part of 64.54 cfs for stock and domestic use estimated to be about 0.76 cfs. Supplemental 1919 right does not include McCully Creek.


Decree (1905 & 1919 rights):

An undefined amount for stock and domestic use estimated to be about 0.76 cfs plus an undefined flow needed to keep ditches from freezing during the winter. Out of stream domestic use is estimate to be negligible during non-irrigation season. Total use is estimate to be less than 1.52 to 2.28 cfs, 2 to 3 times the estimated minimum.

Current ditch management limits this to water intercepted north of Ferguson Creek in the winter.


Permits (1941 & 19761/ rights):

91.41 cfs from McCully Creek, including

2.28 cfs primary rights and 89.13 cfs supplemental rights.


Permits (1941 & 1976 rights):

46.21 cfs from McCully Creek, including

1.14 cfs primary rights and 45.05 cfs supplemental rights.


Permits: No diversion allowed.

Permits (19122/, 19132/, 19172/ & 19211/ rights):

Undefined McCully Creek contribution to 22.21 cfs diverted into Sheep Creek Ditch, including 2.29 cfs primary rights and 19.92 supplemental rights.


Permits (1912, 1913, 1917 & 1921 rights):

Undefined McCully Creek contribution to 22.21 cfs diverted into Sheep Creek Ditch, including 2.29 cfs primary rights and 19.92 supplemental rights.


Permits: No diversion allowed.

Total Right:

114.57 cfs from 1877, 1941 & 1976 rights, plus an estimate of 0.85 cfs for stock and domestic use from 1877 and 1905 rights, plus undefined 1905 and 1919 diversion rights for irrigation.



Total Right:

57.79 cfs from 1877, 1941 & 1976 rights, plus an estimate of 0.85 cfs for stock and domestic use from 1877 and 1905 rights, plus undefined 1905 and 1919 diversion rights for irrigation.



Total Right:

Estimated to be between 0.85 cfs and 2.55 cfs for stock and domestic use, with about 0.18 to 0.27 cfs assigned to McCully Creek diversion #1 and 1.52 to 2.28 cfs assigned to McCully Creek diversion #2.




1/ 1877, 1921 & 1976 rights are believed to be diverted from the stream diverted at McCully Creek diversion #1, somewhere along the stream as it flows through the Prairie Creek drainage.
2/ 1905, 1912, 1913, 1917, 1919 & 1941 rights are diverted from McCully Creek diversion #2 on Sheep Creek Ditch (Wallowa Valley Improvement District canal).

Tim Bliss of the Wallowa-Whitman National Forest has conducted an exhaustive evaluation of water rights, water use, and associated allocation of McCully Creek water in an attempt to define watershed boundaries occurring within the National Forest. Findings from the assessment are listed below and in Appendix C.

(1) The Forest has some stream survey data for McCully Creek above Point A. Terry Carlson, Wallowa Mountains Zone Hydrologist, has estimated Q bankfull to be between 110 cfs and 120 cfs, with a range of 91 cfs to 170 cfs, depending on the variables and equations used. This estimate of bankfull flow closely matches water rights of about 114 cfs for the April 1 to July 31 period which are diverted at Point A (refer to Table 6).

(2) Oregon Water Resources Department has not developed Water Availability Tables for McCully Creek. Oregon Department of Fish and Wildlife has not filed for an instream water right on McCully Creek.
(3) Domestic use is mentioned on the 4 1877 water rights and the 1905 right, but the number of households is not. The watermaster indicates OWRD assumes one household per property. There are 4 properties on the 1877 rights. If one assumes one property per 160 acres on the 1905 right, there would be 32 properties. Total estimates households would be 36. If one uses the current state allowance of 0.01 cfs per household for domestic use expanded, which includes a ½ acre of lawn & garden irrigation, this right would be only 0.36 cfs.
(4) Stock use is mentioned on 5 water rights, but the number of livestock is not. If one assumes each of the 36 properties (identified for the estimate for the domestic rights) has 139 cows, there would be 5,000 cows requiring a flow of 0.50 cfs, plus enough water to prevent freezing of the streams and ditches in the winter.
(5) Information in Table 6 suggests the stream is fully to over-appropriated during the irrigation season. This means landowners have the right to divert all flow for irrigation use from April 1 through October 15.
(6) It is unclear if the stream is fully appropriated during the non-irrigation season. Answers to some questions are needed.


  • Should the upper diversion be treated as a diversion, or as the natural flow of McCully Creek into Prairie Creek? (Locals treat the upper diversion as a natural stream).

  • What is the mean monthly flow of McCully Creek at the upper and lower diversions? Is there any data? (There may be some data for Sheep Creek Ditch
  • How much water is diverted by the upper and lower McCully Creek diversions in comparison with the estimate of 2.0 cfs needed for domestic/stock use?


  • Should any unappropriated flow during any month continue to flow into Prairie Creek, or be diverted back into the old McCully Creek channel below Sheep Creek Ditch?

(7) Bill Knox, ODFW fish biologist comments that the changing of the McCully Creek boundary might complicate efforts to return flow below the two out-of-basin diversions.


(8) Rick Lusk, Baker County Watermaster (former Union/Wallowa County Watermaster) comments that OWRD still treats McCully Creek as part of the Imnaha subbasin; it is part of the Imnaha Decree. Changing the boundary might confuse water rights issues.
(9) Coby Menton, NRCS comments that Prairie Creek is on the 303d List. NRCS is studying water delivery from Sheep Creek Ditch (Wallowa Valley Improvement District Canal). A gage was installed on the canal in June 2000 just above the blocked McCully Creek turnout (McCully Creek diversion #2). The low flow was 1.4 cfs on October 17. There is no gage on the upper diversion (McCully Creek diversion #1), which should be diverting more water. The Wallowa Valley Canal is providing only about 10% of augmented flow of Prairie Creek; the rest of the water is coming from Wallowa Lake/Wallowa River.
(10) Ralph Browning, Fish Program Manager, Wallowa-Whitman NF comments that the USFWS would like to reconnect the bull trout population in upper McCully Creek with other populations in the Imnaha River subbasin. NMFS would like to reconnect the steelhead population in lower McCully Creek with former habitat in upper McCully Creek. The consultation watershed boundary between the Wallowa and Imnaha subbasins includes McCully Creek as part of the Imnaha subbasin. It would appear best to leave McCully Creek in the Imnaha subbasin, even though the watershed delineation protocol suggests otherwise.

There are 59 water rights on the Imnaha River mainstem for a total of 37.33 cfs. Out of this total, the Lower Snake River Compensation Program (LSRCP) chinook hatchery facility will use 15 cfs in a non-consumptive manner. There are an additional 69 water rights on tributaries (excluding the Big Sheep system) for a total of 24.98 cfs. There are 18 water rights on Big Sheep Creek for a total of 6.36 cfs and 5 additional water rights on tributaries (excluding Little Sheep Creek) for a total of 1.65 cfs (this does not include the Wallowa Valley withdrawals). There are four additional water rights filed on springs for 0.29 cfs. In Little Sheep Creek there are 13 claims for 22.47 cfs, 19.6 cfs of which will be used by the LSRCP steelhead facility in a non-consumptive manner. There are an additional 11 claims on tributaries for 26.55 cfs and eight claims on springs for 0.41 cfs. This equals a combined water right of 279.61 cfs (including the Wallowa Valley diversions), 34.6 of which is non-consumptive. There are an additional 36 recent filings that have not yet been approved. In 1955 the legal means to reserve instream flows was created with the passage of the “minimum stream flow law” (ORS536.300-310). This law recognizes water requirements of fish and wildlife as a beneficial use of water and establishes a “public water right” to minimum stream flows to be designated by the state Water Resources Board (Nelson et al 1978 as cited in ODFW et al. 1990c). In 1961 minimum flows were established in the Imnaha River at the USGS gage for 85 cfs. Prior to 1987, established minimum flows were not, technically speaking, water rights and could be revised, suspended, or withdrawn by administrative rule. Since 1987 these minimum flows could be converted to legal water rights with a priority date the same as the date the flows were established. Minimum flows were established for Big Sheep and Little Sheep Creeks in 1993 (Table 7), but they are ungaged. All minimum flows were converted to instream water rights on February 1, 1989.

Table 7. Minimum instream water rights (cfs) at the confluence of Big Sheep Creek and the Imnaha River (reproduced from Wallowa County and NPT 1993)




Monthly Flows (cfs)

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sept

Oct

Nov

Dec

Big Sheep

25

25

30

45

45

37

55

55

55

37

37

25

Little Sheep

10

10

13

20

20

13

13

10


10

10

10

10



Streamflow Restoration Priorities

ODFW and OWRD have established priorities for restoration of streamflow from consumptive users, as part of the Oregon Plan for Salmon and Watersheds (Measure IV.A.8). ODFW has identified the “need” for streamflow restoration through ranking of biological and physical factors, water use patterns and the extent to which water is a primary limiting factor (Figure 8). OWRD ranked the opportunities and likelihood for achieving meaningful streamflow restoration. Rankings were performed for subwatersheds at approximately the fifth field hydrologic units (HUCs). OWRD Watermasters will incorporate the priorities into their fieldwork activities as a means to implement flow restoration measures. The “needs” priorities will be used by the Oregon Watershed Enhancement Board as one criterion in determining funding priorities for enhancement and restoration projects. Watershed councils and other entities may also use the needs priorities as one piece of information determining high priority restoration projects.


Barriers

Diversions for the Wallowa Valley Improvement Canal influence Big Sheep Creek, Little Sheep Creek, Salt, Cabin, Redmont, Canal, and Ferguson Creeks (Nez Perce Tribe et al. 1990). Along Big Sheep Creek, fish habitat quality is reduced or eliminated due to low flows below the Wallowa Valley Improvement Canal diversion dam and diversion dams that are migration barriers (Nez Perce Tribe et al. 1990). Similar impacts on habitat from the canal diversion dam occur along Little Sheep Creek (Nez Perce Tribe et al. 1990). The impacts on fish habitat from reduced flows on these streams were identified as needing further study (Wallowa County and Nez Perce Tribe 1993). Except for one, all diversions in the subbasin covered by the Mitchell Act have NMFS approved fish screens (B. Smith, ODFW, personal communication February 5, 2001). Diversions on non-anadromous streams are not covered by the Mitchell Act and therefore lack screens. Some diversions without screens occur on Little Sheep Creek and McCully Creek (B. Smith, ODFW, personal communication February 5, 2001). None of the diversions that are a part of the Wallowa Valley Improvement Canal contain fish screens.

Information on road culverts acting as fish barriers are unknown for private lands, but three have been identified on National Forest land in tributaries of the Imnaha (Wallowa-Whitman National Forest 1998). These include:


Natural barriers (not related to irrigation projects or impoundments), such as inadequate streamflow, excessive gradient, or elevated stream temperatures may prohibit or prolong adult migration in certain areas of the subbasin at certain times of the year. Although the high gradient reach above the Blue Hole may limit passage of adult spring chinook during some years (Ashe et al. 2000), a more consistent migration impediment is excessive stream temperatures (NPT 1999; Huntington 1993). Elevated summer water temperatures in the Imnaha River below Freezeout Creek may limit the upstream migration period for spring chinook, thereby effectively preventing use of spawning and rearing habitat in that section of river (Carmichael 1993 cited in Huntington 1993).




Figure 8. Streamflow restoration priorities in the Imnaha subbasin (ODFW, 2001




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