Small Decentralized Hydropower Program National ... - Cd3wd.com

disefiar correc’tamente 10s sistemas sin considerar
todos 10s factores hidrokgicos.
Para determinar simplernente ia cantidad potential
de hidroenergia disponsible, todo lo que un hidr6logo
necesita es, como anotamos en la primera. Sec.&n,
conocer el flujo de las corrientes de1 tie y la caida.
Revisaremos mtis adelante las diversas ticnicas
existentes para determinar las corrientes de ;io; la
ca-ida disponible inicialmente es ~610 una aproxima-
ci6n con datos preliminares estimativos tomados por
lo comun directamente de 10s mapas. Las caidas
actuales disponihlw bajo diferentes condiciones de
flujo de la corriente es una fun&n de1 disefio de la
represalreservorio y de las alternativas de opera&n.
Hasta que el esquema regulador de las corrientes
no es+k finaiizado, uno sdlamente puede aproximar el
nivel dt la capacidad instalada y su correspondiente
producci6n de energia. No obstante, tales aproxima-
ciones son importantes para dar asesoramientos
preliminares (niveles de reconocimiento) para deter-
minar si es aconsejable continuar adelante con las
investigaciones. Debe tomarse en cuenta tambi& que
la capacidad de1 reservorio para insta!aciones hidro-
ekctricas peqiiefias son usualinente pequefias, lo que
sign&a que en la mayoria de tales proyectos la
operaci6n de la planta aprovechara !a corriente del
ti0.
Otros factores hidrometereoldgicos de cierta impor-
tancia son la precipitaci6n pluvial, la presi6n de1 aire
(obviamente relacionada a la elevaci6n de1 proyecto),
y aquellos otros factores relacionados con la evapora-
ci0n. En algunas partes de1 mundo, principalmente
donde la superficie de 10s reservorios es bastante
g-rande, la perdidas causadas por la evaporaci6n
pueden ser significativas. Los datos sobre la
precipitaci6n pluvial cobran mayor importancia en
aquellos lugares donde la informacibn sobre las cor-
rientes no existe o es muy limitada.
Los factores relacionados con la caiidad de1 agua
son tambien importantes para 10s esquemas de1
disefio. Se debe considerar cuidadosamente
sedimentaci6n de 10s reservorios. La calidad qtimica
de1 agua es importante, principalmente de1 punto de
vista de la erosidn y iambi& para determinar si el
agua es adecuada para la lubricaci6n de 10s
rodamientos. El agua con elementos corrosives puede
sustancialmente acelerar el proceso de ahuecamiento
causado por la cavitaci6n lo mismo que 10s efectos de
10s materiales erosivos.
La existencia de mapas topogrtiicos facilitan
enormemente la colocacidn precisa de 10s proyectos.
Adem&, ayudargn a identificar las lineas de trans-
misidn existentes (donde ias haya), ubicaci6n de las
28
the dam/reservoir design and the operation
alternatives.
Until the stream regulation scheme is finalized,
one can only approximate the level of installed
capacity and corresponding energy output. Never-
theless, such approximations are important in
giving preliminary assessments (reconnaissance
level) as to the advisability of proceeding further
into the investigations. It should also be noted
‘that the reservoir capacities for small hydro
installations are usually small, meaning that.
most such developments will be run-of-river
operations.
Other hydrometeorologic factors that may be
of importance include precipitation, air pressure
(obviously related to the elevation of the develop-
ment), and those other factors related to evapora-
tion. In some areas of the world, particularly
where reservoirs with large surface areas might
be involved, the losses due to evaporation may
be significant. The importance of precipitation
data is greatly increased where flow data is
missing or limited.
Water quality factors may also be important in
the design schemes. Sedimentation of reservoirs
Imust be carefuliy considered. The chemicai
quality of the water becomes important primarily
from the standpoint of erosion and whether or
not the water is suitable for bearing iubrication.
Corrosive water can substantially accelerate pit-
ting damage caused by cavitation as can the
effects of erosive materials.
The existence of topographical maps will
greatly facilitate precise location of
developments. They will, in addition, aid in identi-
fying existing transmission lines (where they may
exist), gauging station locations, access,
interference with roadways, railroads, etc. Such
information may be very valuable in making
preliminary subjective economic decisions con-
cerning site selection.
The value of short records of hydrologic data
can often be greatly enhanced if there exists a
network of gauges. Obviously one cannot retro-
actively create such networks. It is therefore
important that such acitivities be given serious
consideration immediately.
In its “Guide to Hydrometeorological
Practices”, the World Meteorological Organiza-
tion (1970) offers many practical guidelines to
subjects that will be of interest to hydropower
engineers, with reference to the previous discus-