Skip to content. |
Skip to navigation
Gila River IHA Analysis Jan 24 2013.pdf
1530 kB (1566992 bytes)
I applaud the posting of this "complete and stand alone" document. It is the way each and every thing posted to the web site for public viewimg, reviewing,and commenting should be done. Gerald Schultz
GERALD’S CURSORY REVIEW OF TECHNICAL MEMORANDUM “INDICATORS
OF HYDROLOGIC ALTERATION AS A TOOL IN ECOHYDROLOGIC ASSESSMENT
AND APPLICATION TO THE GILA RIVER NEAR-RIVER GROUNDWATER ZONE”
SENT TO THE NM ISC ON JAN 24, 1013
This Technical Memorandum is somewhat detailed and it is implied in the Background Section that this was the intent, i.e., to not to “oversimplify” in view of the implied nature of the AWSA projects. However, an abundance of data can sometimes lead to oversimplification if a lot of the data is just “hanging in there” and not being “sorted” in a way that provides the best use of it. (The large number of graphs for various flow regimes and situations seems to indicate that all the data was “successfully used” to this end).) Good statistical software has always been around to test for the significance of data.
I did not take the large amount of time needed to review this memorandum in great detail and just did a cursory review in view of the fact that it is well written and the purpose appears to be adequately achieved. I did not look at each and every graph and table for anything that would stand out like graphs having blips and seemingly unexpected “trace paths”. These are computer generated and if the input data was accurate and accurately handled, then the output should follow “suit”. My earlier career was doing these kinds of things by hand and errors could be committed at any step.
Are IHA’s ever used to obtain some flow level, like augmenting the flow from one stream to that of another? This is sometimes done for water supply projects. Also, using the IHA’s for reservoir releases to obtain a desired level commensurate with what is needed for some water species for food, breeding conditions, and bottom conditions?
P1, lines 9 & 10: “. . . before and after flow altering events such as dam construction”. There are man-made events such as dam construction and there also the day to day changes in a stream. Before a dam is constructed, the engineers go through a large amount of simulated flow conditions for the full range of inflow into and out of the dam. They had to follow some rigid rules of environmental flows and dam releases for other purposes. When it comes to the natural flows, how do you use the IHA’s as an assessing tool? If the stream goes dry, I would think that the ecological impacts would be very obvious. Many streams in TX (where I once worked for the USGS) have sandy bottoms that are constantly changing, but the ecological relationship is also a parallel changing thing. I would tend to think the use of IHA’s would be more applicable relevant to man induced changes than natural events. (This was very definitely the situation several years ago in the Rio Grande regarding the Silvery Minnow – but in some what an opposite way. The river was almost at a zero flow level which was too low for the minnow and releases had to be made from upstream reservoirs for its survival. I can see how the use of IHA’s would have predicted this relationship.) This assumes the flow alterations also include quality of the water which in many instances is more important than the quantity of the water.
P6: “Environment al Flow Component Analysis”—“Extreme Low Flows”. I need a better definition for this flow level. Sometimes base flows are given a 2.3-year frequency level; so I would assume any flows below this level could be taken as the extreme low flows. Would this include just reaches of a stream where flow occurs, i.e., water may be in the stream, but below the stream bottom, it will appear again for a short distance, and go back underground. This condition occurs in some sandy bottom or Karst-conditions channels. I note on page 9 that it says that thee flows are below those at the 10th percentile. Is this standard or just for the Gila River in this study?
P7: “Relating IHA to Reach Specific Conditions in the Gila-Cliff Valley.” “. . . for period of record 1937-2001.” Why not include through 2011 or 2012 (if available)? Do you need flow years and not the drought years? Droughts of 1930’s, 50’s, and 70’s were included.
Did you for the 65-year period account for the increasing diversions and other purposes? I note that the storage data at the San Carlos Reservoir was used. Hwy 70 crosses the Gila River upstream from the
Reservoir at a location where there is a huge amount of trees and other growth in the very wide river channel (or a major braided situation). This growth has been increasing during the 65 year time period and a lot of water gets lost through transpiration. Was this accounted for?
P12, par 3: “. . . Class 1 (unimpacted condition) to Class 5 (severely impacted condition).” I assume Class 5 has a lot of influence from man. Are natural flows included in these categories? I would tend to think that a naturally occurring large flood inflicts impacts, yes, but they are still natural and I would not classify them as either a good or a bad thing. People’s viewpoints differ on this – some think large natural floods are a good thing while others think they are bad. When the Teton Dam located in ID was breeched many years ago and caused loss of life as well as widespread damage, an IHA, if in existence then, would have probably given a Class 5 to a potential dam breech; something I expect would be done to all dams. However, I understand in a 100% natural system, there is a need to know how IHA’s work. And I also fully understand why the IHA use in the AWSA CUFA is needed; however, if there is a peak flow of 20,000ft3/s and the full 350 ft3/s is taken out, is it really possible to see the different ecological impacts from the 20,000 ft3/s or the resulting 16,500 ft3/s?
P14, last par: “Evaluations to assess impacts . . . associated with CUFA diversions.” and “If these analyses and identification of specific . . . additional round of focused evaluation may be pursued.” I completely agree with both of these statements as it illustrates the IHA process is still in an ongoing developmental status. I can easily see that to use “specific and limited” elements is important to get reliable IHA’s or “better control of input data is always more desirable”.
Written and submitted by:
NM RC&D Activities
On the Portal:
only in current section
On our Partner Search:
Advanced Partner Search
New Mexico Interstate Stream Commission
P.O. Box 25102
Santa Fe, New Mexico 87504-5102
Telephone: (505) 827-4059 | Fax: (505) 827-6188
Email: Beatriz Vigil, NM Interstate Stream Commission (email@example.com)