THE PROJECT ON IRRIGATION SCHEME DEVELOPMENT IN CENTRAL AND EASTERN UGANDA
VOLUME-III ATARI IRRIGATION SCHEME DEVELOPMENT PROJECT (F/S)
CHAPTER 3 FACILITY PLAN FOR ATARI SITE THE PROJECT ON IRRIGATION SCHEME DEVELOPMENT IN CENTRAL AND EASTERN UGANDA FINAL REPORT VOLUME-III ATARI IRRIGATION SCHEME DEVELOPMENT PROJECT
CHAPTER 3 FACILITY PLAN FOR ATARI SITE
3.1 Intake Facility
3.1.1 Head Works
(1)Intake Facility from River
Intake structures made of reinforced concrete will be provided at a place just upstream of the existing weir site and water will be distributed through the main canal along national road and foothill of both banks.
The Atari River specific discharge can be estimated from a regression of the Sipi River specific discharge.
Table 3.1.1 Estimation of Discharge at the River
Item Unit The Sipi River Atari Site Catchment Area km2 92.00 103 Ratio 1 1.12 Past max. Discharge m3/sec 11.411 12.78 Ordinary discharge m3/sec 1.71 1.915 Drought Discharge m3/sec 0.23 0.26 95 days discharge m3/sec 3.64 4.76
On the other hand, probability flood discharge with ten years returns period is calculated at 38.00 m3/sec.
Within this project, a weir made of reinforced concrete with steel plate gate will be constructed so as to roughly adjust intake discharge and to flow down floating particles or mud through gate except during drought period. The weir is attached with spillway which is able to flow down relatively moderate flood water so as to minimise gate operation. Flow depth of spillway will be limited to 0.30 m so as not to raise the water level of the river above the existing ground level. Gate will be fully opened when floods occur.
Intake gates will be installed in order to adjust intake water precisely.
(2)Width of Scouring Sluice Gate
The width of scouring sluice gate will be decided from allowable flow velocity over reinforced concrete i.e. Vmax. =3.0 m/sec in accordance with the following formula and actual width of the existing river.