Scientific Investigations Report 2006–5036
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5036
The main flow channels entering and leaving the refuges that have been continuously monitored are the Ady Canal at State Line Road, Klamath Straits Drain at State Line Road, and D Pumping Plant on the edge of Tule Lake Sump 1A. Monthly records for all three sites go back as far as 1962 in the BOR hydrologic database. The accuracy and quality of the measurements and the records were assessed because of their importance in determining refuge water use.
Flow data collection at these three sites is serviced by the BOR, USFWS, Klamath Drainage District, and TID. Overall flow-record documentation for these sites is limited, as the records have not been compiled, reviewed, and published on an annual basis. It was not possible to document how every flow record value was computed. Annual station analyses for the sites were nonexistent. (Recently, however, the USFWS has improved flow-measurement accuracy at the Ady Canal site.) Daily values at all three sites were not computed from unit (hourly) values. Although continuous strip charts were used at the Klamath Straits Drain site to estimate head differences, only a single head difference value was taken (manually) from the charts for each day.
The rating the USGS uses to describe the accuracy of an annual streamflow record depends on (1) the stability of the stage-discharge relation or, if the control is unstable, the frequency of discharge measurements and (2) the accuracy of measurements of stage, measurements of discharge, and interpretation of records (Herrett and others, 2004). An “Excellent” rating indicates that about 95 percent of the daily discharges are within 5 percent of the true value. A “good” and “fair” rating indicates that about 95 percent of the daily discharges are within 10 and 15 percent of the true value, respectively. Records that are considered to be less accurate are rated “poor.” Different accuracies may be assigned to different parts of a record. Because the USGS flow-record rating is applied to a record on an annual basis, it can be changed from year to year. For this assessment, the ratings, presented in the following sections for each of the flow gages, also were based on current conditions of the instrumentation, record compilation methods, and the existence of documentation regarding how every daily value was computed. Accuracy ratings for the three sites are shown in table 8. In addition to USGS ratings, accuracy ratings that were assessed by the California Polytechnic State University Irrigation Training and Research Center are also shown (Burt and Freeman, 2003).
The Ady Canal structure at State Line Road consists of four Waterman 48” circular canal gates. The two east gates divert water to Unit 2 in the refuge and generally are open. The two west gates divert water through pipes to Unit 5a and the Sheepy West unit, and generally are closed from April–September. Upstream and downstream water levels are measured by two staff plates. The plates generally are read on a weekly basis, or whenever the gate openings are changed by USFWS or BOR technicians. Flows are computed using a modified version of the Waterman gate flow equation. Input variables to the equation are the gate opening and the head difference between the upstream and downstream water levels.
In 2000, the USFWS made a series of check measurements at the site on the downstream side of State Line Road. (Check measurements are direct measurements of flow that are used to verify the accuracy of flow estimates made with the use of rating curves or other indirect methods.) The USFWS made an additional check measurement on September 12, 2005. Measured flow was 115 ft3/s. With the measurements, it was possible to construct a relation between the flow measurements and estimated flows using a canal gate equation (Tim Mayer, U.S. Fish and Wildlife Service, Portland, Oregon, written commun., 2005).
The USGS made a check measurement at this site on August 24, 2005, on the south side of State Line Road using an acoustic Doppler current profiler. Measured flow was 123 ft3/s. The flow computed from the USFWS canal gate equation using a gate opening of 18 in. and head difference of 3.4 ft at the time of the measurement was 135 ft3/s, which is an overestimation of approximately 10 percent.
To rate the current flow record for the Ady Canal site, various factors were considered. The most critical factor is that there is no continuously operating instrumentation at this site. Data are acquired by reading staff plates. However, in examining records in the BOR office in Klamath Falls, there was no evidence that the staff plates and gate openings were read and recorded on a daily basis; nonetheless, individual daily flow computations using the equation were still made. This site also did not have ideal cross-section locations that are needed to make accurate check measurements. Because of these factors, this flow record was rated as “poor.” In other words, 95 percent of the daily flows could be in error by more than 15 percent.
The Klamath Straits Drain structure at State Line Road consists of three canal gates. Similar to the Ady Canal gates, flow is computed at this site using the gate openings and the upstream and downstream head difference. Unlike the Ady Canal site, there are two Stevens drum-type stage recorders mounted on stilling wells upstream and downstream of the gates. Continuous recorders make it possible to compute daily flows with more reliability. At the time of this study, flows at this location were close to zero, and it was not possible for the USGS to make a check measurement. It could not be determined when the last check measurement was made at this site and by what agency.
On the basis of most factors, this flow record could have been rated as “fair,” in which case 95 percent of the daily flows would have been defined as being within 10 to 15 percent of true flow. However, the flow record for this site did not have adequate documentation of how each daily flow value was determined. For this reason, the flow record was rated as “poor,” indicating that 95 percent of the daily flow values could have been in error by more than 15 percent.
The D Pumping Plant has five pumps. Pumps 1, 2, and 3 are rated by the manufacturer as having a pumping capacity of 160 acre-ft/d (80.7 ft3/s), and pumps 4 and 5 have a pumping capacity of 142 acre-ft/d (71.6 ft3/s) (Ron Fensler, Tulelake Irrigation District, Tulelake, California, oral commun., 2005). Although the plant was constructed in the 1940s, most of the pumps have been replaced or retooled since that time. Daily flow estimates are made by keeping a daily record of the number of pumps in operation and their duration of operation.
On August 3, 2005, the USGS made a flowmeter check measurement of the D Pumping Plant by measuring flow in the P Canal at Doris Brownell Road. Measured flow was 82 ft3/s. However, upstream of the measurement, approximately 1,800 gal/min (about 4 ft3/s) was being pumped out of the canal to a farm field. Without that withdrawal, the flow would have been approximately 86 ft3/s. The flow measurement was rated “fair,” which for individual flow measurements (unlike annual streamflow records discussed above) means that the measurement could have been off by 8 percent of true flow. Actual flow, then, might have been within the range of 75–89 ft3/s. At the time of the measurement, TID was operating one pump continuously for several days. The USFWS also made check measurement at the same location on the P Canal on November 1, 2000, and measured 218 ft3/s. At the time of that measurement, three pumps were operating. BOR records for that date reported a flow of 436 acre-ft/d (220 ft3/s) at D Pumping Plant.
Similar to the Klamath Straits Drain flow record, this flow record also could have been rated “fair.” However, the flow record for this site did not have adequate documentation of how each daily flow value was determined. For this reason, the flow record was rated “poor,” indicating that 95 percent of the daily flows could be in error by more than 15 percent.
In recent years, the need for more accurate flow measurements of water entering and leaving both the Lower Klamath and Tule Lake refuges has become apparent. Following are improvements that could be made to the data-collection network to increase the accuracy of flow measurements. The USGS is aware that some of these improvements already are planned through current collaboration between the BOR and the Irrigation Training and Research Center of California Polytechnic State University.
Data consistency, management, storage, and retrievals would be improved if all refuge boundary flow data collection efforts were performed by a single agency, either the BOR, USFWS, or USGS. All flow records, both past and future, would be archived by and stored at the offices of a single agency.
Proper documentation of all aspects of flow-data collection is essential for maintaining a high-quality data-collection program. It requires the maintenance of an archive for each data-collection site that includes hourly stage values, rating curves, check measurements, stage shifts, rating shifts, and stage measurements, which can be used to recreate any or all of the published daily flow record if necessary.
Digital data loggers are more accurate and reliable than strip-chart stage recorders, which were originally developed in the 1930s. The Klamath refuge data collection program would be much enhanced by the installation of digital data loggers with real-time telemetry at the Klamath Straits Drain flow site, Ady Canal at State Line Road site, the D Pumping Plant, and possible new sites.
Check measurements help verify the accuracy of the flow record at data-collection sites. Depending on the stability of a stream’s channel bed, USGS protocol stipulates that a check measurement be made at each site generally every 3 months. Check measurements made with the same frequency at refuge boundary flow sites would provide a degree of confidence in the quality of the data that would not be possible without such measurements.
The main flow channels near or at the boundary of the Lower Klamath refuge (Ady Canal, D Pumping Plant, and Klamath Straits Drain) already are gaged. However, periodic flow measurements at Sheepy, Cottonwood, and Willow Creeks would increase the accuracy of inflow estimates because the cumulative flow of these streams, approximately 14 percent of inflow to the refuge, is significant.
To further improve the measurement of flow into the Tule Lake refuge, the BOR and/or the USFWS could install a streamflow gage on the Lost River near the entrance of the refuge, if it is feasible. Another possible site for a gage would be at the main points where Project water enters the N Canal. Most of the N Canal water is used to service Sump 3. However, unlike the Lower Klamath refuge, flow comes into the Tule Lake refuge at many locations. Flows at many of those locations may still have to be estimated, because establishing flow gages would not be practical.
For more information about USGS activities in Oregon, visit the USGS Oregon Water Science Center home page.
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