Performance evaluation of two farmers controlled drainage units in Mardanscarp [Pakistan]

In this study two drainage units water table of about 1m and greater than2m were selected. The present study assess some of these areas such thatthose factors may be pinpointed which can help to he improved for remedialpurposes in the system. For this purpose data was collected on croppingpattern, irrigation and drainage, crop water requirement, net irrigationrequirement, supply of irrigation and rainfall etc of the area. These data weretaken for two drainage units of LSV and MGV in Mardan SCARP. The LSVdrainage unit is 40.50 ha. This command area is irrigated through anappropriate proportional model offtake from Nisata Branch Canal (NBC). Some ofits deep percolation collected by subsurface tile drains is delivered toKashmalo open drain. The MGV drainage unit is irrigated through sliding gatehaving variable discharge. The subsurface drainage of this drainage unit isalso delivered to open Kashmalo drain. These both subsurface drainage hadbeen controlled at their exits. The most prominent difference between MGV andLSV is the lease and share cropping. Cropping pattern of kharif season ofboth drainage unite had been collected twice. The first cropping pattern wascollected in July and the other at the end of kharif season in October 1999.Questionnaire proformas were developed for information about land holding,tenancy status; and yield of sugarcane in addition to the cropping pattern.For the estimation of Net Irrigation Requirements and Gross IrrigationRequirements reference evapotranspiration was estimated through CROPWATComputer Program. These values were then utilized to calculate crop waterrequirement. The derived values of crop coefficient (Ke) were used. The netirrigation requirements were calculated by the deduction of effective rainfallof 80%. The gross irrigation requirements were approached through anassumed value of 60% efficiency of the irrigation system. The hydraulicconductivity of both drainage units were determined through Auger HoleMethod also called field permeability. The network of observation wells wasinstalled in both drainage units to study the water table phenomenon. Thesewater tables throughout the area were tested for different operational policiesof flow in the canals adopted for the whole year round. In addition to thelinear relation of water tables with canal operation and seasonal changes, athree-dimensional study of the both drainage units has also been done toassess the given parameters more deeply. Hence a more realistic study ofground water distribution through SURFER Computer Model was possible. Thecontour maps of ground water for both drainage units were very clear. Thedifference in contours were divided among five groups or ranges from lessthan 0.6 to greater than 2m. The percentage area covered by each range wasspecified through planimeter. The yield of sugarcane was related to the rangesof water tables in both drainage units. The area of each drainage unit hadbeen divided into different zone to compare the yield of a zone to the watertable for different operation policies and seasonal occurring. The findings fromall these practices are presented in the conclusions.