Irrigation Water Management Strategy in Rechna Doab using GIS & Modeling Approach

Abstract

Pakistan is an agricultural country and irrigation plays vital role in crop production. Pakistan is blessed with world biggest and oldest Indus Basin Irrigation System (IBIS). Beside the largest surface irrigation network, Pakistan still not meeting the irrigation requirements because of increasing cultivation area to meet the food requirements of rapidly growing population. This system was originally designed for 70-80 percent cropping intensity and currently operating at 150-170 percent cropping intensity. Groundwater is alternated source of water to meet irrigation requirements during low canal supplies and high crop water demand. The crop water demand is increasing from head to tail end perspective whereas annual rainfall, groundwater recharge and canal supply are decreasing in head to tail end. These anomalies in groundwater recharge and discharge has given birth to groundwater depletion at tail reach and waterlogging at the head reach. Therefore, this study was designed to manage surface and groundwater resources to ensure sustainable irrigated agriculture in Rechna Doab area of Punjab, Pakistan. All necessary data were collected from different organizations whereas, field visits and periodic survey were also conducted under ACIAR project for groundwater depth, cropping pattern, groundwater use and surface supplies. A hydrological geo-data base was developed using Arc-GIS computer software and groundwater flow model was developed in Processing MODFLOW. The groundwater flow model was developed for 0.515 million hectares with 1000 m x 1000 m resolution. Model contain 123 columns, 110 rows and four layers. The time variant data of evapotranspiration, river, recharge and tubewell were incorporated for 16 stress periods from kharif 2005 to rabi 2013. Model was calibrated using field data for groundwater heads from year 2005 to 2009 and then validated from rabi 2009 to rabi 2013. Three different pumping scenarios were undertaken from 2013-2037 to understand aquifer behavior for identification of sustainable groundwater pumping zones. Scenario-P involved simulation of current groundwater abstraction for next 24 years. In Scenario-Q, twenty (20) percent more abstraction from fresh groundwater zone and 20 percent more supply to hazardous groundwater zone was simulated. In Scenario-D, twenty (20) percent more abstraction from shallow groundwater zone and 20 percent more supply to deep groundwater zone was simulated. The results showed that 39.6 percent reduction in annual rainfall and 8.3 percent increase in reference evapotranspiration from head toward tail reach of branch canals of study area. Lower Gugera branch canal receives 10-30 percent more supplies at offtake point as compared to Burala branch canal. Variations in flow of distributary channels are found random without any trend in head-tail end perspective. Groundwater depth varied from 1 m to 19.47 m toward tail ends with an average slope of 0.14 m/km. Developed model revealed the improvement in groundwater depth with rate of change of 4.3 x 104 m3/day while total inflow into model domain was about 1.09 x 106 m3/day and outflow was 1.047 x 106 m3/day. Scenario-P revealed that there is no intimidation regarding depletion of groundwater level or expansion in waterlogged area under normal climatic conditions. Predicted results of Scenario-Q revealed that groundwater would decline more rapidly in fresh groundwater zone in the range of 0.22 to 0.33 m/year and groundwater level would rise in range of 0.15 to 0.24 m/year in shallow groundwater areas at the head reach. According to Scenario-D, groundwater would rise in all irrigation administrative units in the range of 0.028 to 0.2 m/year. Study concluded the Scenario-D as most suitable strategy in curtailing the inequity of irrigation water in head-tail end perspective which otherwise stretched due to spatial climatic variability. Present research work will facilitate the Punjab Irrigation Department and policy makers for sustainable solutions regarding groundwater depletion and related issues.