/ HJ{ IGA 77 ON ANU DRAIN A GE. 161 



the crops. The soil excavated is almost all used for 

 increasing the width of canal banks and only a little is 

 required for the drain bank. 



On no account should canal banks be cut to draw off 

 water for irrigation purposes. Earthenware pipes should 

 be used and on the larger canals small regulators of stone 

 or brick masonry should be built, fitted with a sluice gate 

 opened and closed by an iron screw. The screw should 

 have lathe-cut threads, and never be less than one and a 

 half inches in diameter. The waterway of regulators 

 should not be less than one quarter of the waterway of 

 the canals which they supply. 



Canals should be cleared annually of all silt deposit. 

 January is a suitable month for this work as little irrigation 

 is required I)}' crops, and the canals can be closed. If a 

 canal is not carrying sufficient water, opportunity is taken 

 during the annual clearance of deepening the tail-end. A 

 canal 2,500 metres long supplying eight different properties 

 gave, a very poor supply to the last one at the tail end. 

 By deepening it 25 centimetres at the first year's clearance 

 and again another 25 centimetres the second year, it had 

 such a slope that water reached the last property freely. 

 Agricultural canals should have a slope of at least ten 

 centimetres per kilometre = 70000 an d the smaller one at 

 least twenty centimetres per kilometre = 50 -ou- 



Planting canes "Boos" along small canal banks is 

 very advantageous. Their roots strengthen the banks greatly 

 whilst the canes are useful for roofing huts and cattle 

 sheds, and for fencing vegetable plots. They grow quickly 

 and occupy the banks but do not grow in the water and 





