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. PARSONS MEMORANDUM April 2, 2003 To: Larry Lang From: Gary Lewis Subject: Comments on Cherry Creek March 2003 DRAFT Final Report I have reviewed the March 2003 A W A report titled, "Probable Maximum Precipitation (PMP) Site-Specific Study for Cherry Creek Reservoir, DRAFT Final Report" and have the following general comments on the scientific aspects. I have quite a number of marks in the margins of my copy, and can provide copies of the marked pages if you wish. Without listing them here, I have marked a number of locations with the comment "defer to Lou and Nolan." For those categories, I believe that they can provide the most relevant comments, and where they agree, I also agree. The comments below provide my opinions in categories that I believe I am qualified to make. Many of the items in the report are the same as, or slight extensions of, material in Interim Report #1, AWA 4/26/02 Memo For Record, and Interim Report #2 which I've already addressed in my 18 January 2002, 3 May 2002, and 25 June 2002 memos, respectively. These three reports, plus this memo, should be considered my overall response to the study. I believe I have been consistent in all four documents. Please feel free to forward these comments to the other participants as appropriate. General Comments The final report is by far the most organized, complete, and easiest-to-read document produced. I scanned the original "compliance" checklist that you provided to the three reviewers, and conclude that A W A has complied in every practicable way with the scope of work, exceeding the original scope in many critical aspects. A W A notes in their closing remarks that there are three significant differences between the two studies, two of which I discussed in my May 3 memo (spatial within- storm distribution and orographic effects). As I noted earlier, it looks like the spatial distribution issue was assessed in far greater detail by A WA than NWS, rendering it valid because of the generally-accepted notion that any more-detailed study supercedes regional analysis. A scientifically.sound "compromise position" (neutral effects) is being offered on the orographic effects issue. I am giving deference to Lou and Nolan on the third difference, the Palmer/J(jowa barrier moisture depletion. Many of the other 19 secondary issues that I had identified in my 1/18/02 review of Interim Report #1 have been generally addressed. A few questions about some of them are included in my markup of the DRAFT.