Abstract
Medium-resolution satellite images have been widely used for the identification and quantification of irrigated areas by center pivot. These areas, which present predominantly circular forms, can be easily identified by visual analyses of these images. In addition to identifying and quantifying areas irrigated by center pivot, other information that is associated to these areas is fundamental for producing cadastral maps. The goal of this work was to generate cadastral mapping of areas irrigated by center pivots in the State of Minas Gerais, Brazil, with the purpose of supplying information on irrigated agriculture. Using the satellite CBERS2B/CCD, images were used to identify and quantify irrigated areas and then associate these areas with a database containing information about: irrigated area, perimeter, municipality, path row, basin in which the pivot is located, and the date of image acquisition.3,781 center pivots systems were identified. The smallest area irrigated was 4.6 hectares and the largest one was 192.6 hectares. The total estimated value of irrigated area was 254,875 hectares. The largest number of center pivots appeared in the municipalities of Unaí and Paracatu, with 495 and 459 systems, respectively. Cadastral mapping is a very useful tool to assist and enhance information on irrigated agriculture in the State of Minas Gerais.
Highlights
Irrigated agriculture is the major consumer of freshwater resources in the world and it accounts for more than 70% of the water withdrawn from lakes, rivers and groundwater (CAI & ROSEGRANT, 2002).According to OLIVEIRA & TALAMINI (2010), the main methods of irrigation in the Brazilian agriculture are: furrow irrigation or drainage, used in 33.8% of the irrigated area, central pivot, present in 21.8% of the irrigated area, conventional sprinkler, used in 18.8% of the irrigated area, and surface irrigation, accounting for 18.1% of the irrigated area
According to SCHMIDT et al (2004), the margin of error related to counting the number of pivots when using satellite images is not higher than 5%, but it is influenced by image resolution, size of the pivot, cloudiness, image overlapping and the lack of contrast between the occupation and the neighboring soil
We identified 3,781 center pivot systems in Minas Gerais state
Summary
Irrigated agriculture is the major consumer of freshwater resources in the world and it accounts for more than 70% of the water withdrawn from lakes, rivers and groundwater (CAI & ROSEGRANT, 2002).According to OLIVEIRA & TALAMINI (2010), the main methods of irrigation in the Brazilian agriculture are: furrow irrigation or drainage, used in 33.8% of the irrigated area, central pivot, present in 21.8% of the irrigated area, conventional sprinkler, used in 18.8% of the irrigated area, and surface irrigation, accounting for 18.1% of the irrigated area. Irrigated agriculture is the major consumer of freshwater resources in the world and it accounts for more than 70% of the water withdrawn from lakes, rivers and groundwater (CAI & ROSEGRANT, 2002). The method applied in the smallest scale is localized irrigation, equivalent to 7.5% of the irrigated area in Brazil. CHRISTOFIDIS (2008) estimated that, the irrigated area totaled 350,200 hectares in the state of Minas Gerais in 2003/2004, and the method of central pivot irrigation amounted to 89,430 hectares. The author cited that the difficulty in obtaining sufficient water available to meet both the existing areas and for new projects would be one of the obstacles to the expansion of irrigation. With the need for a rational use of water resources for various purposes, remote sensing and geographic information systems (GIS) are important tools for monitoring activities related to water usage, such as irrigated agriculture with central pivot
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