International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
Rainwater Catchment in Agriculture
Peculiarities of Runoff Generation in Deserts (The Kyzylkum Desert as
Sobirjon Azimbaev, Obidjon Azimbaev, Nilufar Turdieva
Institute Of Water Problems
Uzbek Academy of Sciences
The source of nutrition for temporary water drains in Central Kyzylkum
is rain and sometimes thawed snow. Observation of the formation of drains
(G. T. Leshinsky, 1963) shows that water gates, formed by takir and takir
sort soils, precipitation in quantity of up to 3-5 mm for the period of
one rain does not usually cause drains. They are completely spent on infiltration
and for surface detention in microfall comprising so-called initial losses
of drain. At very damp soil or at downpours initial losses are several
times less. So, precipitation in 5 mm with intensity 0,10 mm/mm already
form a drain.
In water gates formed by loamy-sandy soil earth, initial losses of drain
in dry water gates reaches 20-26 mm and sometimes even more. It means
that the intensity of precipitation, particularly in the autumn and spring,
usually does not exceed intensity of infiltration of these soils. In very
moist soil or in downpour the initial losses are less. Research of G.T.
Leshinsky shows, that the precipitation in 5 mm with intensity 0.10 mm/min
already forms drain.
According to the data of Gidrometcenter maximum relative number of cases
of drain-forming rain (8.5-14.3%) is observed under precipitation of 5-10
mm, under precipitation exceeding 20 mm, it is insignificant at less 2
%. A number of drain-forming rains with precipitation more than 5 mm -
from 3 to 8.
Calculations are based on the method of N. M. Alushinskaya (1959) for
possible collection of atmospheric precipitation under their various intensity
in the area situated between mountains Kuljuctau and Auminzatau.
It is clear that the volume of surface drain for one rain (sum of precipitation
- 10 mm, average intensity of rain - 0.5 mm/min) for the water gates with
an area of 2700 m2 equals 518 m3 of water from the same area under the
intensity of rain 0.1 mm/min and 1296 m3 of water can be collected. Similar
calculations are done for the areas with various lithological structure
under the various sums of precipitation per rain and its intensity and
different areas occupied by water gates, in different geomorphological
conditions of Central Kyzylkum.
The use of a small part of potential water resources permits to improve
drinking and pasture water supplies in various desert regions.
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