| Summary: | Agriculture is a very important thing to support a food supply. The
availability of adequate water for crops will give a good results on agricultural
production. To provide sufficient water for plant growth it can be made some
water supply systems by build irrigation systems channels. The purpose of this
research is (1) identify the amount of water availability at Boro Weir, (2) identify
the amount of agriculture water requirement at Boro Irrigation Area, (3) know
the evaluation of water balance between agriculture water requirement and
water availability in Boro Irrigation Area.
Method to identify the number of water availability is use probability
analysis of the Bogowonto streamflow at the Boro weir for 10 years period.
Calculation of water requirement on agricultural lands using the data of air
temperature, solar radiation, wind speed, rainfall, humidity, cropping patterns,
percolation and the area of agricultural land. The amount of water requirement is
identify from the calculation of crop water requirement (CWR), farm water
requirement (FWR) and project water requirement (PWR). CWR calculation
includes calculation of evaporation using Penman method. FWR calculation
includes calculation of effective rainfall use SCS-USDA method and percolation
use Van Genuchten equation. PWR calculation includes calculation of irrigation
channel efficiencies use inflow-outflow method. Evaluation of water balance is
made by comparing the number of water availability and agriculture water
requirement.
The results showed that the water supply increased in the rainy season with
the highest value occured in February at 26517,71 liters/sec and decreased
during the dry season with the lowest value occurred in August at 354,33
liters/sec. The number of irrigation water requirement for paddy-paddy-palawija
cropping pattern get the highest value on paddy planting season that occured in
May I at 5804,24 liters/sec and get the lowest value on palawija planting season
that occured in September I at 67,68 liters/sec. The results of water balance
analysis between water supply and agriculture water requirement indicates there
is shortage of water requirement that occurred in October I at 1372,59 liters/sec,
October II at 1044,12 liters/sec, May II at 969,27 liters/sec, June I at 2215,11
liters/sec and June II at 465,95 liters/sec.
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