Micro Catchments-An Efficient Water Conservation Technique in Rainfed Areas
(Muhammad Nasir*, Hafiz Muhammad Arslan Abid, Sajjad Manzoor, Muhammad Tayyab)
University of Agriculture, Faisalabad, Pakistan
A micro catchment is a specially designed area with slope to increase runoff from rain and concentrate in a planting basin where it infiltrates and remains available to plant for its subsequent use.
Micro catchment has several advantages such as,
- They provide moisture to the plant with little efforts and can be developed using manpower
- Many crops and plants can be grown using micro catchments
- They increase soil fertility by trapping the organic matter coming from catchment
Micro catchments can be of different size and shapes depending on soil structure/texture, plant type, slope, effective rainfall etc. These shapes can be of square, rectangular, triangular, V-shape and semi-circle/half moon or C-shape
For design of a micro catchment the ratio of catchment area (C) to cultivated area (CA) is important. Catchment area is the one from where runoff is generated and transported under the slope to the cultivated area where plant has been planted. The following formula can be used to calculate C/CA.
C: CA varies from 1:1 to 3:1 but in low rainfall areas it exceeds up to 10:1
- Design Rainfall is effective rainfall which should be more than 5mm.
- Runoff coefficient is ratio between runoff and rainfall which depends upon soil type, slope and vegetative cover etc and its value varies 0.1 to 1.0
- The efficiency factor includes variations in field structure and slope and its value ranges from 0.5 to 0.7
Typical Values of Runoff Coefficient
Basin Characteristics Runoff Coefficient
Sandy Soils covered with bushes 0.10
Sandy Soils covered with light bushes 0.20
Loamy soils largely cultivated 0.40
Clayey Soils stiff and Bare 0.90
Design micro catchment for olive trees if annual rainfall is 300mm and annual water requirement for olive is 600mm. Assume efficiency factor is 0.7 and runoff coefficient is 0.5
Crop water Requirement= 600mm
Design Rainfall= 300mm
Runoff coefficient= 0.5
Efficiency factor = 0.7
According to formula,
- How to measure Catchment Area and cultivated Area?
It can be measured by using following formula,
A square shape catchment has an area of 400 ft2 and radius of the cultivated area is 4 ft, calculate C/CA?
So Catchment area is 7 times of the cultivated area.
How to measure slope?
Slope can be measured by using following formula
h= height from ground surface to bund of catchment
d= distance from base of tree to the bund of catchment
Height can be measured by placing a rod from bund of catchment till base of the tree, as catchment area is relatively more slope than cultivated area so a leveler is placed over the rod where it become level that height is recorded
Radius is measured from base of the tree to tree canopy, take a stone and drop it from above canopy where it falls that will be the canopy area
Research work is going on in “Barani Agricultural Research Institute” (BARI) and “Soil and Water Conservation Research Institute” (SAWCRI) Chakwal under the project of “Watershed Rehabilitation and Irrigation Improvement in Pakistan” with the objective to conserve the soil and water in rainfed areas of Pakistan.