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utilizaran los resuitados. Se puede crear un modelo
de energia bastante simple, que se utiliza para
a&lisis de1 preliminares potential, basado en obser-
vaciones fluviales cotidianas durante el period0
registrado (aproximadamente, 365N &as, donde N es
el nlimero de ties registrados). Debemos tomar en
cuenta, que con este metodo “cotidiano” de an$lisis se
sumergen 10s ties de bajo-flujo y 10s periodos de
bajo-flujo dentro de un afio en un solo registro total.
Los porcentajes indican el promedio de la frequencia
relativa s6lamente d--u-ante el period0 registrado.
Cuando se utihka +a1 procedimiento es conveniente
mostrar hidrogr&ficas anua!es tipicas tambikn para
que se puedan iderkificar 10s periodos criticos con-
tenidos dentro de1 afio. (Figura 2).
El mismo procedimiento, con las mismas limita-
ciones puede ser efectuado utilizando valores pro-
medio mensuales. El registro en este case consistirh
de 12 N puntos de informaci6n. Debido a que 10s
valores promedio mensuales van a camuflar las varia-
ciones que ocurren dentro de1 mes, la curva de
duraci6n fluvial tend& una apariencia distinta de la
de1 anklisis fluvial cotidiano, y coma resultado sera
menos titil en la consideraci6n de1 disefio. Natural-
mente que 10s mismos argumentos se pueden
esgrimir para las curvas de duraci6n fluvial derivadas
de valores promedio anuales.
Debido a que las corriente en ciertos lugares
especificos obedecen a variaciones ciclicas coma
funci6n de periodos dentro de1 tie, se puede derivar
un valor mayor si el anglisis es basado en duraciones
fluviales mensuales. Esto se puede hater por lo
menos de dos maneras. En una, se ordenan todos 10s
promedios de enero (por ejemplo) coma una serie de
datos de valores N, y se hate el anrilisis. Sin
embargo, hay que tener presente que al utilizar 10s
promedios mensuales, &tos van a enmascarar las
variaciones que ocurren dentro de1 mes. Por lo tanto,
un aklisis de todo el flujo cotidiano durante enero
(en este ejempio) va a resultar en una mejor base
para la consideracidn de1 diseiio. Dependiendo de1
prop6sito de1 analisis puede que ~610 se necesite
evaluar 10s periodos mensuales criticos (10s que para
unidades pequeAas de hidroenergia deben incluir 10s
petiodos de alto flujo al @al que 10s meses obvious
de bajo flujo).
Otro procedimiento podria ser el de intentar desar-
rollar ties “indices”, En c:ste procedimiento se
prepara primer0 la curva de durci6n fluvial anual. De
aqui se puede identificar el tio indice K-percentile.
Usando 10s datos fluviales histciricos, mensuales y
cotidianos, que ocurrieron durante 10s afios indices
46
the corresponding 20 to 30 percent exceedance
flows.
More often than not in developing countries,
the data for site hydrologic analyses will be quite
limited. Even in the United States, a country that
by general standards could be considered to
have a wealth of data, it is almost always
necessary to adjust remote information.
The recently completed study at the Idaho
Water Resources Research Institute (Gladwell, et.
al., 1979) had as one of its goals a complete
hydioelectric potential analysis of the Columbia
River system in the United States. We chose to
use the daily flow-duration procedure with ac-
companying average annual hydrographs. Since it
appeared evident that such a task would greatly
exceed our capability to depend upon “nearby”
gauges, a different aproach was called for. A
regionalized approach was developed that
included availability of an estimate of mean an-
nual precipitation values. The procedures used
permitted the development of synthetic flow-
duration curves at any point on any stream in the
region, within the constraints of the process.
This, in combination with the site physical data
allowed the calculation of the potential energy
under a series of assumed installed capacity
levels.
If records are to be compared with each other
or used in regional analyses, they should of
course represent concurrent periods. It is impor-
tant that the differences in records reflect those
of climate and/or drainage basin characteristics
and not simply those of different time periods.
Even if no regional studies are contemplated, it is
important to extend the records, if it is possible
to add information by so doing. Techniques were
discussed earlier concerning the general subject
of extending records and filling gaps.
A method for directly extending flow-duration
curves has been suggested ivy Searcy and
Hardison (1959). In this procedure, called the
index-station method, a relationship is esta-
blished between two stations. The procedure
begins by using the data of the overlapping time
period to derive two flow-duration curves. The
pairs of discharges corresponding to given
exceedance percentages are then plotted against
each other (as shown in Figure 5). The graph for
this short period is assumed to represent the
relationship between the two stations and, thus,
would correspond for the longer period. If this is