Devaluating Drainage Design Parameters for the Fourth Drainage Project, Pakistan by using SWAP Model: Part I – Calibration

A transient drainage simulation model,SWAP, was used to evaluate the performanceof drainage systems in (semi-) arid zones.Before application, the model wascalibrated by using 14-months datacollected from two sample fields of theFourth Drainage Project (FDP), Punjab,Pakistan. During the calibration process,emphasis was given to the accuratedetermination of soil hydraulic parameters,reference evapotranspiration, drainage fromsample fields and bottom boundarycondition. Laboratory determined soilhydraulic parameters were foundnon-representative of the field conditions.Difference between laboratory and fielddetermined soil water retention curves werefound significant. The pressure heads andsoil water contents measured in depthincrements of 15 cm were in good agreementwith the simulated values after applying afield measured retention curve. A closeproximity was also found between measuredand simulated average root zone salinity at0–1.0 m depth. The referenceevapotranspiration calculated by thePriestly-Taylor (PT-ET _o) methodwas found physically more realistic thanthe Penman-Monteith (PM-ET _o)method due to ignorance of the feed backmechanism of vapor pressure deficit onstomatal closure. The simulated cumulativedrainage from two sample fields wascomparable with the calculated values. Theanalysis of piezometer data shows thatthere is a negligible water exchangebetween the deep aquifer and theunsaturated zone. Therefore for scenarioanalysis, no flow conditions at the bottomof the soil profile can be applied as abottom boundary.     

Asset Management for Irrigation and Drainage Infrastructure – Principles and Case Study

This paper presents the general principles and functions of asset management for irrigation and drainage infrastructure: Asset planning and creation strategies, operation and maintenance, performance monitoring, accounting and economics and audit and renewal analysis. The various elements of the program are conceptually defined and their application is illustrated with the asset management program (AMP) formulated for the La Khe Irrigation System in Vietnam. It also identifies the role of the AMP within the framework of service oriented management of irrigation and drainage services. An infrastructure and investment profile developed from the asset survey identified the investment requirement over the next 40 years. The analysis of cost of service and revenues shows a shortfall of US£17.00/ha/annum to meet the investment requirement over this period. The asset audit and renewal analysis shows the upgrades of the main system needed to improve the current level of service.