Performance Evaluation of Two Irrigation Systems Using Geographic Information System and Remote Sensing

Abstract

Perhaps the most important yet limited resource on earth is water. Only 3% of water on Earth is freshwater two-thirds of which is frozen in glaciers and polar ice caps, the rest comprises the surface and ground water available for human consumption. Water sustainability has been a perennial concern of all nations. Its availability over the years has dwindled immensely leading for the agriculture sector to suffer in terms of its productivity.

In the Philippines, irrigation has been the major agricultural technology utilized to grow essentially all kinds of crops. Being an agricultural country, our economy greatly relies on available water in order to produce the increasing demand in food and other daily necessities. Irrigation development accelerated after the creation of NIA in 1963; however many of the schemes developed are now aging and have accumulated damage through natural calamities such that they are not able to fulfill the expected functions. Many systems now require comprehensive and systematic upgrading to bring them to full operating status. Thus, in order to ensure sustainability it is important that irrigation systems should be evaluated to check and improve its performance (ADB 2008).

The study aims to compare and assess the performance of two irrigation systems of the National Irrigation Administration. The assessment would identify the old and/or present method of the agency and compare it to a new method developed using Remote Sensing and Geographic Information Systems tools. The study was conducted in two areas in Laguna Province through ground validation, interviews of the agency’s focal persons, farmer association members, as well as collection of secondary data.

Different performance indicators were used, to wit: Relative Water Supply, Relative Irrigation Supply, Water Productivity, and Standard Gross Value of Production. Results Concluded that there is a great positive gap between the water supply and demand for the crops.

The result of the assessment shows that the water use indicator has a gap between crop demand and water supply. Computed RWS and RIS values of 1.19 and 1.18 respectively will indicate excessive water supply.

The computed RWS and RIS values for the study is about 0.75 and 0.80 respectively. This may be called deficit irrigation practice. This means that NIA’s irrigation systems are oversupplying water to their rice fields. It could also be an indicator that the area receives abundant water supply during wet season, which they are not able to store for the dry season that is why irrigation is still needed. Averaging their respective RWS and RIS shows that BRIS was able to supply a little less than CEPIS.

Amidst this, water productivity is very low. This is because irrigation supply is too high as compared to its capability to produce meaning both irrigation systems are supplying around 75 percent more than the rice field needs.

Despite the oversupply in irrigation, high production of rice leads to high standard gross value of production (SGVP). Though CEPIS yield production was only 0.65 ton/ha behind the great difference in cropped area, leading to a very high difference of SGVP between CEPIS and BRIS. With all the indicators computed it was concluded that BRIS is more productive than CEPIS.