Analysis of Susceptibility to Degradation of Water Ecosystem Services as a Tool for Land Use Planning: a Case Study in a Small Brazilian Watershed.

Mapping priority areas for environmental conservation and restoration is essential to informing policy formulation and decision-making. This study proposes a methodology based on multicriteria analysis and on-site assessment to develop environmental zoning that enhances the provision of water ecosystem services (WES) from Brazil's Água Quente River Basin. Integrated analysis of multiple criteria enabled identification of degrees of susceptibility to degradation, assessment of effects of land-use changes between 1990 and 2020, and validation of the study's methodology via field protocol. The results indicated that the spatial and temporal patterns of WES susceptibility to degradation varied little within the study area with the most critical levels occurring primarily in the Agua Quente's floodplain, where there are sandy textured soils and coverage with a low degree of soil protection. Zoning analysis designates 40% of the basin`s area as consolidated use, 28% for environmental conservation, 19% as anthropic use, and 13% for environmental restoration. Field analysis indicates that the occurrence of degraded areas and pollution by solid waste and urban effluents are relevant factors that affect the basin's water resources. Linear regression analysis indicated a good fit between the data modeled by the multicriteria analysis and those observed on-site (R² = 0.6 p < 0.05). The study's method is effective and its structure can be used in other river basins, as its approach is simple and flexible and can be readily adjusted to fit the characteristics of the study site.

Integrated empirical models to assess nutrient concentration in water resources: case study of a small basin in southeastern Brazil.

A significant contributor to water pollution is increased nutrient concentration that results in eutrophication. Modeling approaches are crucial to understanding the dynamics of nutrients in river basins. This study integrates empirical models into Geographic Information Systems to quantify total nitrogen and phosphorus (TN and TP) load and concentration in watercourses of Brazil's Lobo Stream Hydrographic Basin (LSHB). Land use, topographic, demographic, and hydrological data were used to simulate the load and concentration of nutrients generated by point and nonpoint pollution sources. The results indicate that the simulated TN and TP load is primarily generated by nonpoint sources, 81% and 76%, respectively. The Itaqueri River subbasin is the most critical, yielding more than half of the basin's TN and TP load. About 90% of annual LSHB point pollution load is generated in the Itaqueri River subbasin, principally from the Água Branca Stream. The linear regression between simulated and observed concentration indicates significant relationships (TN, r2 = 0.73 (p < 0.05), TP, r2 = 0.78 (p < 0.05)). The method used was able to simulate TN and TP concentration in watercourses, but was inconsistent for point pollution, indicating it represents the dynamics of nutrients in rural basins more effectively than in urban ones. The study shows that its methodology, despite limitations, enables scientists and managers to understand and predict spatial distribution of nutrient concentration in LSHB watercourses.