EP 1110-2-9
31 Jul 94
(d) Estimate future irrigation depletions.
(2) Download data from various sources.
(e) Compute changes in irrigation: future-historic.
(3) Rough check data viability by display or screen-
ing processor.
(f) Prepare final computation of corrected flows.
b. Process hydrologic data for model input (stream-
(g) Produce display statistics of final irrigation quan-
flow data). This is a very important and potentially
tities to be used.
time-consuming step in which a uniform database of
streamflow is derived, to be used as inflows in reservoir
(6) Prepare final computations; display and check
regulation models. Although monthly data are typically
data and formatting for model input.
used, a shorter time period (daily or more frequent) may
have to be developed if flood regulation analysis is
(a) Perform checking computations to check data
involved. Take full advantage of HEC-DSS-linked pro-
validity (e.g., compute locals).
grams (STATS, DSSMATH, etc.) to evaluate and process
data.
(b) Prepare final production of statistical summaries,
displays.
(1) Perform cross-station checks such as double-mass
plots to reveal record inconsistencies. Evaluate and cor-
(c) Prepare final formatting for model input.
rect as necessary.
c. Derive synthetic (stochastic) monthly flow record
(2) Decide on period of record to be used, consider-
ing data availability and incorporation of significant
(optional). In addition to the historic period of monthly
flows, it may be desirable to employ a synthetic flow
events.
sequence, derived by stochastic techniques. This would
be particularly important when multiple-year critical peri-
(3) Estimate missing data.
ods are being encountered.
(4) Compute storage changes at upstream reservoirs.
(1) Consult with HEC and others on best available
Adjust historic records to remove effects of historic
upstream reservoir regulation.
programs and techniques to derive a stochastic flow
record, given the basin configuration and analysis
(a) Convert elevations to storage, if necessary, for
requirements.
each project.
(2) Review technical publications; find examples of
(b) Calculate adjusted streamflow at downstream
applications.
stream gages.
(3) Obtain computer programs, run on test data.
(c) Accumulate storage adjustments where more than
(4) Determine scope and cost of work and benefits
one reservoir is involved.
of using stochastic record.
(d) Produce tabulations, statistical summaries for
(5) Prepare input to stochastic flow generator as pro-
checks.
gram requires.
(5) Process/estimate irrigation depletion data. Correct
(6) Analyze output to ascertain its statistical sound-
historic records for changes in irrigation diversions.
ness. Revise input as needed.
(a) Review irrigation records; determine magnitude of
impact on study.
d. Derive historic or synthetic flood flows. A water
supply investigation or storage allocation study may
(b) Decide on scope of effort.
require analysis of flood control criteria. If so, historic
and/or synthetic flood hydrographs are needed. Examples
(c) Compute year-by-year historic diversions and
of synthetic floods are design floods such as the Standard
return flows.
Project Flood; or, different spacial and temporal flood
F-2
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