IRRIGATIE UIT EEN MOERAS Een hydrologische studie van de ...

working out the irrigation possibilities of the swamp (Chapter 8).
Possibilities of the swamp as an irrigation reservoir
From the calculation model for possible irrigation use the following limitations of
the use of the swamp as a reservoir appear:
- The storage capacity is limited by leakage loss
- Its filling is entirely dependent on rainfall
- The surface is very large in relation to its depth, causing high evaporation loss
- At low levels the vegetation adversely affects the flow resistance, by which means an
•important part of the water reserve becomes available only slowly.
The successful development of rice cultivation is largely due to the fact that the
average rainfall in Nickerie is fairly well spread throughout the year. The storage
capacity of the swamp is sufficient most years to bridge a short dry-spell. In addition
the flexibility of water use in rice cultivation must be an important factor in making
this success possible.
The use of water in rice growing appears to be largely dependent on the cultivation
plan. This provids the desired water control in the plot. In the large scale rice scheme
in Wageningen (Foundation for Mechanized Agriculture in Suriname) this cultivation led
to a definite peak in water use. In the small scale agriculture in Nickerie, however,
the decision on sowing time and mid-season drainage is made individually by 3000
farmers, which means the demand for water is more evenly spread over the growing season.
Together with this fact, there appears to be a connection between the average water demand
and the level of the swamp.
The farmer tries to arrange his growing plans to reduce the chance of crop failure
as much as possible. The damage which may result from limited availability of water has
not been adequately investigated.
A verdict on the total area irrigable from the Nanni swamp can currently only be
given on the basis of a subjective view of the effects of a water shortage on production.
Because of irregular rainfall patterns from year to year uncertainty exists as to the
filling of the swamp. This could be reasonably clarified however, by calculation of the
water balance for a great number of years, with the aid of stations such as Apoera and
Paradise, which already have a long series of observations.
Enlargement of the capacity of the swamp as an irrigation reservoir might be carried
out in various ways:
- By reduction of the flow resistance at low water levels, by keeping the Nanni creek open
and the contraction of channels to draw water from the swamp.
- By restraining the leakage into the Corantyn river at times of high swamp levels.
- Enlargement of the catchment area, by channeling drainage from the southern area
in the direction of the Nanni zwamp.
- By including water from the 'Zanderij' area in the supply to the swamp. It may be
expected that this area could supply water in dry periods from the ground water reservoir.
The water gain can be estimated partly from this publication; for design purposes
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