The effects of the equitable canal water allocation model scheduling on crops and soils under the Warabandi water management system : a case study of the Hakra Branch Canal command area of the Punjab Province Pakistan.
Thesis DisciplineWater Resource Management
Degree GrantorUniversity of Canterbury
Degree NameMaster of Water Resource Management
Agriculture is the mainstay of the economy of Pakistan and accounts for 21% of the Gross Domestic Product (GDP) and 80% of the export revenue. It also employs about 48% of the labour force in the country. Punjab province is considered to be the bread basket of Pakistan by virtual of the crop produces as it accounts for 83% cotton, 80% wheat, 97% rice , 63% sugarcane and 51% maize, all of which are grown under irrigation. There are a number of constraints that the irrigation system faces that include design constraints, water availability constraints, conveyance losses, soil salinity, sodicity, sedimentation and financial crunches. Most of these constraints would require the government to rethink how the irrigation system works in order to overcome them. For example, to overcome the design constraints, land reform might be necessary (not very popular), massive investment would be required to upgrade the conveyance system to reduce system losses while due to increase in population and climate variability, water availability can only get worse. The easier way for the time being is to try and ensure equitable distribution of the water available among the farming community through development of better irrigation and service interruption scheduling techniques. The Equitable Canal Water Allocation (ECWA) model has been developed to ensure equitable water distribution by proper scheduling of service interruption. Several scheduling scenarios have been developed but their effect on crops and soils is unknown. AquaCrop, a crop water productivity model, has been used to investigate the effects of these scheduling scenario as it is cheaper and faster when compared to practical implementation in the field. Three scheduling scenarios that have been investigated are: Punjab Irrigation Department (PID) Scenario (status quo), Scenario A (most inequitable) and Scenario I (most equitable). These scenarios have been applied to cotton and wheat across different planting dates as practiced on the ground in order to determine their effects on achievable yield, conjunctive water use, root zone depletion and salinity build in the soil profile. A comparison between on achievable yield, conjunctive water use, root zone depletion and salinity build has shown that there is minimal variation between PID scenarios and both Scenario A and I. This could be interpreted to mean that it is possible to enhance equity of water delivery without necessarily affecting on achievable yield, conjunctive water use, root zone depletion and salinity build. It is worth noting that planting early in the season has been shown to yield more than planting late in the season, but other factors (labour, machinery and certified seed) might prevent early planting.