Compensatory forestation for soil water retention in watersheds of Campos do Jordão municipality, SP, Brazil

Abstract

Compensatory forestation is an important technique to estimate the necessary forest cover for compensating the water loss due to surface runoff within a watershed and, therefore, guiding forest recovery interventions. The objective of this study was to quantify the forest area needed to compensate water loss caused by surface runoff in Fojo Creek and Perdizes Creek basin areas in the municipality of Campos do Jordão, SP, Brazil. Estimates were based on the Compensatory Forestation Methodology for Retention of Rainwater in Small Watersheds, which takes into consideration the average total annual precipitation, land cover and land use, the water infiltration capacity of soil, and an international recommendation indicating that 20.55% of the water in the hydrological cycle should infiltrate into the soil. These two watersheds have a total area of 2,666.6 ha that account for 9.3% of the municipal area of Campos do Jordão. The main land use and land covers in this area are: 1,257.9 ha of forest, 434.4 ha of urban area, 432.5 ha of commercial forest plantation, 265.1 ha of highland prairies, 126.8 ha of pastureland, and 149.9 ha of other classes. Water infiltration rate field experiment estimated a high rate (298 mmh-1) in forested areas, 289 mmh-1 in areas covered by commercial plantation, 94 mmh-1 in highland prairies, and 63 mmh-1in pasturelands. Based on the 20.55% infiltration recommendation of precipitated water, it was estimated that the total forest area required for these two watersheds to compensate for the runoff caused by the other land cover classes (prairies, pasture lands, reforestation plantations and urban areas) should be 1,318.1 ha (51,8%). Therefore, an additional 60.2 ha of recovered forest is needed to compensate for the loss of 1,096 million m³/year of water lost in theses watersheds.