The Science of Instream Flows A Review of the Texas Instream Flow Program (2005) / Chapter Skim
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6 Implementation Issues
6 Implementation Issues
Pages 110-128
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From page 110... ...
, but the Texas instream flow documents hardly address the critical issue of how the instream flow recommendations will be implemented. Implementation issues will be especially important to the Texas instream flow program because it is expected that the state and its citizens will take a number of years to develop and refine mechanisms for instream flows and sound ecological environments in the state's highly diverse river systems.
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From page 111... ...
briefly discusses the use of models in implementation. This chapter also highlights the importance of adaptive management and on-going peer review, and considers some of the technical recommendations from previous sections of the report in the context of implementing both the state-wide program and flow recommendations for specific river systems.
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From page 112... ...
As a watershed is converted from its natural vegetative cover into urban areas or farms, infiltration capacity of the watershed is reduced, leading to increases in high flow pulses and overbank flows and decreases of subsistence and base flows. A sound instream flow recommendation will need to anticipate these types of future changes in hydrologic conditions, so that water managers can implement necessary modifications to water management practices or make permitting decisions consistent with instream flow goals.
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From page 113... ...
Another way to use available water for instream flow purposes is through increased efficiency measures. Other states have encouraged water uses to implement efficiency measures, and Texas could use these existing examples as a guide for its instream flow program.
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From page 114... ...
These sister state programs reinforce the notion that instream flow programs can be implemented even in highly arid regions. Other states' programs also represent a significant reservoir of experience and expertise that Texas policy makers can consult in moving forward (e.g., continued participation in the Instream Flow Council)
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From page 115... ...
. A potentially important consideration in a program with tiered implementation, such as the instream flow program in Texas, is that as demand for water increases, it will be difficult to implement instream flow recommendations on second and third-tier rivers.
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From page 116... ...
The first example shows how instream flow goals could be attained through permitting activities; the second highlights the importance of flow variability in instream flow recommendations; and the last example shows how models can be used to restore targeted flows. The first example is from Texas.
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From page 117... ...
to the City of Victoria in 1996 for withdrawals from the Guadalupe River affords a significant degree of protection to instream flows (including subsistence flows, base flows, high flow pulses, and overbank flows; see Box 6-1) with the effect of protecting instream flows in a manner similar to the "percent of flow approach." Although not initially intended as an instream flow effort, the City of Victoria permit shows how instream flow recommendations could be implemented in Texas.
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From page 118... ...
TABLE 6-1 Flow Statistics for the Guadalupe River at Victoria by Month Month Normal Flow (cfs)
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From page 119... ...
Implementation Issues 119 The method used to define normal flows is a combination of the Lyons Method based on monthly median flows, and ecological flow needs of the Guadalupe Estuary as follows: "normal flows, based on gaged records, will be described as 40% of the monthly median streamflow in the months of Oc tober through February; 60 percent of the monthly median flow in months of March, April, July, August and September; and a flow rate for the months of May and June based on a prorated share of the minimum flow values calcu lated to maintain beneficial inflows for the living resources and ecological in tegrity of the Guadalupe Estuary." Moreover, the "low flow" is defined as the "amount of flow for each month needed to protect water quality in the river, and to a limited extent provide, on a short-term basis, dissolved oxygen lev els for sustaining fish and wildlife species." Figure 6-1 provides a graphical interpretation of these diversion limitations. FIGURE 6-1 Graphical representation of diversion limitations for the Guada lupe River at Victoria, TX.
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From page 120... ...
It is clear from the monthly base flow summaries that current base flow conditions occasionally drop below the targeted levels, and at other times are higher than specified by the instream flow recommendations.
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From page 121... ...
. For purposes of statewide water planning and water permitting in basins for which detailed instream flow studies have not been conducted, a statistical hydrology method may better characterize normal monthly base flow and high flow conditions.
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From page 122... ...
The SWFWMD has estimated that the selected restoration projects could provide as much as 75 cfs of additional flow to the upper Peace River during a 90 day low flow period. Some of these measures include: CONTINUING REVIEW OF THE PROGRAM An instream flow program has scientific parts that nest within a policy context.
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From page 123... ...
SOURCE: SWFWMD 2002, 2004 of the instream flow program over time, just as the initial peer review was designed to provide, "the highest level of confidence for all interested and affected parties that the framework within which these studies will be carried out is scientifically sound." In order to fulfill this comprehensive program objective that involves scientists from a variety of disciplines, state agencies, and other stakeholders, the creation of an independent, interdisciplinary, periodic peer review process for the instream flow program is recommended. POLICY CONTEXT FOR TECHNICAL RECOMMENDATIONS In the proposed revised instream flow framework (Figure 4-2)
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From page 124... ...
However, they must be applied care fully to ensure that they generate instream flow estimates that are consistent with instream flow protection goals. For example, in Figure 6-2, the median base flow levels for each month for the Guadalupe River at Victoria are shown, along with a line representing the average high flow pulse level.3 The base flow values have been estimated using a "base flow separation technique" which separates the river's base and subsistence flows from high flow pulses and overbank flows caused by rainfall events.
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From page 125... ...
In sum, hydrologic desktop methods such as the Lyons Method or CCEFN that are based on monthly medians may lead to inconsistent and unreliable protection of base flows while generally under-protecting high flow pulses and overbank flows. Hydrologic desktop estimates can be improved by first applying a base flow separation analysis to the daily data series, and then computing estimates of normal base flows or high flows separately, as illustrated in Figure 6-2.
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From page 126... ...
From the review of the water quality models used in the Texas total maximum daily load program, the recommendation was made that the instream flow program should be integrated with the water quality, water permitting, and other water-related programs in Texas. Several waterrelated programs already exist at the state level, including those associated with water quality, streamflows, bays and estuaries, and water permitting.
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From page 127... ...
water. Three examples of successfully implemented instream flow recommendations underscore a range of important issues such as using permitting to achieve instream flow goals; the importance of flow variability in implementing instream flow recommendations; and use of hydrologic simulation models in flow restoration projects.
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From page 128... ...
Stakeholder involvement is discussed in Chapters 3 and 4 in the context of setting goals and building public support for instream flow work; stakeholder involvement in this chapter is acknowledged as important element in realizing the implementation of an instream flow recommendation. Finally, a recommendation was made in Chapter 5 to integrate the instream flow program with water quality, water permitting and other water-related programs in Texas.
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