Environmental Engineering Reference
In-Depth Information
Mill Creek dye study, Station 4
August 28-30, 2006
Pearl River County, Mississippi
6.00
5.00
4.00
3.00
2.00
1.00
0.00
19:55:12
22:19:12
24:43:12
27:07:12
29:31:12 31:55:12
Elapsed time (h)
34:19:12
36:43:12
39:07:12
41:31:12
43:55:12
FIGURE 4.15 An example of a dye time-concentration curve. (From MDEQ, Time-of-travel of water trac-
ing dyes in MS streams, Mississippi Department of Environmental Quality, Jackson, MS, 2007.)
and then dividing that into the product of the mass of dye injected and the dye's speciic gravity,
as described by Kilpatrick and Cobb (1985). Figure 4.16 illustrates some of the common results
of dye studies.
Dye studies are often extremely useful in river studies. They allow measurements of lows where
the standard method, as described previously, is not applicable. They also integrate the results of the
river's features over their travel distance, thereby providing a good estimate of the average veloc-
ity, rather than a point velocity. Dye studies may also provide measures of mixing and dilution. A
limitation is that they provide data only for the time and conditions under which the study is done,
so they cannot be easily extrapolated to other conditions.
4.3.6 M eaSureMent of f LowS b aSed on H ydrauLIc S tructureS
The low in reservoirs, many rivers and streams, and some estuaries is controlled by structures
such as dams or weirs. In controlled releases, such as for hydropower, the releases are directly
measured. In uncontrolled releases, such as over a spillway or an emergency spillway or through
an oriice, the low can be estimated from the type of structure and the water surface elevation.
Uncontrolled structures, such as weirs, are often placed in channels for the purpose of measuring
lows, and an example is the V-notch weir illustrated in Figure 4.17. A number of methods for mea-
suring lows using culverts, weirs, lumes, and other hydraulics structures are well described in the
USGS Techniques of Water-Resources Investigations Reports. Book 3 Applications of Hydraulics ;
Section A: Surface-water techniques (http://water.usgs.gov/pubs/twri/). The water measurement
manual from the Bureau of Reclamation (2001) also provides a detailed discussion of measurement
methods, and programs are available such as the Bureau of Reclamations WinFlume to aid in the
design and analysis of lows from lumes and weirs as described by Clemmens et al. 2001.
4.3.7 f Low In u nGaGed r IVerS
There are many locations on gaged streams for which lows are not known and many ungaged loca-
tions, and, unfortunately, the number of such locations is increasing. For these locations, it is often
necessary to estimate the low or some low characteristics. One common method is to use regres-
sion equations, which relate some streamlow statistic to basin characteristics, such as (Ries 2002)
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