Section 6. Violations of Instream Flow Rules

Human demands for freshwater resources need to be balanced with the ecological needs of river and estuarine systems (Petts 2009). Instream flow rules, which allocate specific flow and timing regimes in rivers and river system, are meant to legally account for the ecological requirements that may have previously been unconsidered. The Washington Department of Ecology (Ecology) and Department of Fish and Wildlife (WDFW) have developed instream flow rules to “protect and preserve instream resources” (Washington State Department of Ecology 2004), that include fish and fish habitats, water quality, wildlife, aesthetics, and recreation. Instream flow rules are developed by a defined scientific methodology (Washington State Department of Ecology 2003). They do not affect established (senior) water rights or withdrawals. They can limit future (junior) surface water withdrawals, or withdrawals from ground water that is in hydraulic continuity with the surface water, in order to protect minimum instream flows. Instream flow rules may also limit maximum withdrawals or establish closures where it has been determined that there is no water available for further appropriations.

Instream flow rules do not affect exempt groundwater withdrawals^{[see comment pending review]}, including:

• Stockwatering;
• Single or group domestic, up to 5,000 gallons per day;
• Industrial purposes, up to 5,000 gallons per day; and
• Irrigation of up to one-half acre of lawn or non-commercial garden (see Revised Code of Washington [RCW] 90.44.050).

Instream flow rules exist for many of the rivers and streams within the Puget Sound. Table 1 shows a summary of Instream Flow Rules for basins surrounding the Puget Sound by Water Resources Inventory Area (WRIA).

Alterations of the natural flow regime affect river ecosystems by changing physical habitats, including patterns of longitudinal and lateral connectivity, and by altering the natural cues and patterns of biological response, which could adversely affect native species that have evolved in response to historical flow patterns. Alterations could enhance the success of invasive or introduced species in a river system (Bunn and Arthington 2002). Due to the complexity of natural flow regimes, the establishment of simplified instream flow rules based on minimum flow requirements or rules of thumb may not be protective of natural resources; i.e., it is not clear whether instream flow rules are protective of native flora and fauna (Arthington et al. 2006, Naiman et al. 2008). Several studies have suggested the adoption of flow rules and management targets that are more considerate of all aspects of the natural flow regime (Bunn and Arthington 2002, Arthington et al. 2006, Naiman et al. 2008, Petts 2009, Poff et al. 2010).

A measure of the management effectiveness of freshwater resources is to compare actual instream flows with the instream flow rules. A high percentage of instream flow rule violations could indicate an over-allocation of freshwater in a basin. An increasing trend in violations could indicate that the freshwater demands are increasing. For the purposes of this report, violations were determined by comparing the instream flow rules to the average daily flow at specified gauging stations. A violation was noted when the average daily flow was less than that specified in the instream flow rule. The average percent of violation days per month were calculated for the time period of the instream flow rule. Trends were evaluated for the period from October to June or during the typically water-critical period from July toSeptember (see Table 2). Trends were determined by simple linear regression over time; trends significantly different that zero (P<0.05) were noted..

Violations for instream flow rules were calculated for eight rivers, with the intent of evaluating at least one river or stream from each of the WRIAs in the Puget Sound watershed. The selection of rivers is shown in Table 1.

Table 1. Summary of Instream Flow Rules for Water Resource Inventory Areas (WRIA) surrounding the Puget Sound.

None of the river systems evaluated consistently met the instream flow rules (Table 2). In five of the eight river systems, there were at least two months per year when actual flows did not meet the instream flow requirements at least 50% of the time. Flows in the Stillaguamish River failed to meet instream flow rule requirements 90% of the time during the July-August-September period. This is the highest percent of violation of any river evaluated.

Table 2. Summary of percent violations of Instream Flow Rule for selected rivers in the Puget Sound. Period is effective dates of Instream Flow Rule. Violations occurred when average daily flow at gauging station was less than value specified by Instream Flow Rule. Overall average for the time period and annual percent change are shown. Water Resources Inventory Areas that are not shown do not have established Instream Flow Rules.

Generally, the highest percent of violation of instream flow rules occurred in August and September. There were no significant trends of the percent violations of the instream flow rule over time for any of the river systems evaluated (P>0.05).

This analysis uses average daily discharge data from the eight USGS stations specified in Table 2 (United States Geological Survey 2010b). The datasets include qualification codes indicating whether data are provisional or have been approved (United States Geological Survey 2010a). We avoided using provisional data in this analysis, and we omitted data from gauging stations for which advisory notes warning against unreliable data quality had been posted.The gauging stations on the NF Stillaguamish River near Arlington (USGS 12082500) and the Nisqually River near National (USGS 12082500) advised of poor data quality during storms or high flow conditions. High flow conditions would not result in violations of the instream flow rules and so this did not affect the analysis.

The development and application of Instream Flow Rules is relatively recent (see Table 1). Consequently, most stations offer only a limited number of years from which to evaluate data. The relatively short time period and high interannual variability precluded detection of significant long term trends.

All streams showed violations of the instream flow rules, most commonly occurring in August and September. Notably, flow levels in the Stillaguamish River were below instream flow requirements approximately 90% of the time during the summer months. The Puyallup River exhibited the lowest percent of instream flow rule violations of any river evaluated. The monthly average percent violations did not exceed 25% for any month of the water year.

Arthington, A. H., S. E. Bunn, N. L. Poff, and R. J. Naiman. 2006. The challenge of providing environmental flow rules to sustain river ecosystems. Ecological Applications 16:1311-1318.

Bunn, S. E. and A. H. Arthington. 2002. Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30:492-507.

Naiman, R. J., J. J. Latterell, N. E. Pettit, and J. D. Olden. 2008. Flow variability and the biophysical vitality of river systems. Comptes Rendus Geoscience 340:629-643.

Petts, G. E. 2009. Instream Flow Science For Sustainable River Management. Journal of the American Water Resources Association 45:1071-1086.

Poff, N. L., B. D. Richter, A. H. Arthington, S. E. Bunn, R. J. Naiman, E. Kendy, M. Acreman, C. Apse, B. P. Bledsoe, M. C. Freeman, J. Henriksen, R. B. Jacobson, J. G. Kennen, D. M. Merritt, J. H. O'Keeffe, J. D. Olden, K. Rogers, R. E. Tharme, and A. Warner. 2010. The ecological limits of hydrologic alteration (ELOHA): a new framework for developing regional environmental flow standards. Freshwater Biology 55:147-170.

United States Geological Survey. 2010a. Provisional data for Washington.

United States Geological Survey. 2010b. USGS Washington Water Science Center.

Washington State Department of Ecology. 2003. A Guide to Instream Flow Setting in Washington State. Water Resources Program, Olympia, WA.

Washington State Department of Ecology. 2004. Setting instream flows and allocating water for future out-of-stream uses. Olympia, WA.