Time space analysis of dams in the State of Pará in the last 20 years

The identification of the reservoir sites of water bodies is of utmost importance for the study and management of water resources. However, the registration of such information in a continental country like Brazil is still done in a merely informative way by the owners of these reservoirs. The on-site registration by the inspection and environmental agencies such as the National Water Agency (ANA) demands a high cost, besides taking a long time to be carried out, generating delays, outdated registration, or lack of information, which can bring consequences in the efficient management of water resources in the municipalities. The present work has as its main objective to carry out the mapping of the dams in the entire state of Pará, which have an area of water sheet greater than 3,600 m2. A temporal analysis of their construction over the last 20 years (1999–2019) was carried out using Landsat 5 and Landsat 8 satellite images with the MNDWI index method; to compare the records generated with the official records, as well as to study the factor influencing the appearance of these new dams. The results obtained showed a significant increase of 656 % in new dams or reservoirs in the last 20 years. A total of 3704 dams were identified in the State of Pará; however, only 314 dams are registered on ANA's website, representing a rate of only 9 %. Also, it was noted that the exponential increase in this number occurred in mesoregions where agribusiness activities are practiced, such as cattle and soybean farming. Thus, the results can serve as support to the inspection agencies in identifying the most critical sites that need to be inspected.