ABSTRACT Considering the importance of topographic surveys to determine soil volumes and study efficient and accessible alternatives for this operation, this study aimed to analyze methods and respective equipment for planialtimetric surveys to determine soil volume. An experimental grid was installed in an area locate in Fernandópolis, SP, Brazil, in which quotas were measured by geometric leveling (standard method), trigonometric leveling, leveling with receivers of the Global Navigation Satellite System (GNSS) by relative (frequencies L1/L2) and absolute positioning (code C/A) and extraction of altitudes in digital terrain model from SRTM and ASTER images. In comparison to geometric leveling, trigonometric leveling was the most accurate in determining soil volume (0.6% error), followed by GNSS leveling by relative positioning (23.7% error), and extraction of altitudes by SRTM (32.0% error) and ASTER images (38.3% error). GNSS leveling by absolute positioning presented the highest error in determining soil volume (287.4%) compared to the other methods.

ABSTRACT Without effective actions to improve environmental management, water resources tend to become scarce. Thus, this study aimed to understand the processes influencing the physical, chemical, and biological properties of the water due to land uses and occupation in the Ipê stream basin, in Ilha Solteira - SP (Brazil), regarding the dependence of the analyzed variables. Monitoring of chemical, physical, and biological water quality was performed from 2006 to 2011, and the records of land use and occupation in 2011. A factorial multivariate analysis allowed us to understand that the processes in densely populated areas increased degradation of water by the input of organic loads, yet those of farming areas enhanced the degradation of the chemical and physical quality of spring waters. Therefore, installing irrigation systems near populated areas, for crops consumed in natura, may compromise this agricultural activity, as well as the absence of water filtration systems downstream agricultural areas. Furthermore, we concluded that multivariate statistics is a powerful tool to detect these influencing processes in water quality. In this study, this type of analysis played an important role isolating the processes acting on water quality.

O assoreamento é um processo natural, mas que pode ser potencializado pelas ações antrópicas e resulta em grandes problemas para os reservatórios, reduzindo seu volume útil para a irrigação. Um exemplo deste problema foi a redução da área do espelho d'água da represa municipal de Fernandópolis em 48,3%, durante 20 anos. Por isso, este trabalho teve como objetivo avaliar a produção de sedimentos e o assoreamento da represa municipal de Fernandópolis a partir de metodologia que pode ser aplicável a pequenas barragens de terra para fins agrícolas. Para isto, foi monitorado, mensalmente, durante um ano, o volume de sedimento depositado na represa. O percentual de retenção de sedimentos na represa municipal de Fernandópolis variou de 53,9 a 94,5%, que associada a uma alta produção específica de sedimentos, provocará seu completo assoreamento em, no máximo, 57 anos. Recomendam-se para minimizar este processo, a restauração das áreas de preservação permanente e a retirada de 17.500 m³ de sedimentos do leito da represa.

The siltation is a natural process, but can be accelerated by human actions and results in major problems for the reservoirs, reducing its useful volume for irrigation. An example of this problem was the reduction of the area of mirror water of Fernandópolis municipal dam in 48.3% during 20 years. Therefore, this study aimed to evaluate the production of sediments and siltation of Fernandópolis municipal dam from a methodology that can be applied to small earth dams for agricultural purposes. For this, it was monitored, monthly throughout the year, the volume of sediment deposited in the reservoir. The percentage of retention sediment in Fernandópolis municipal dam ranged from 53.9 to 94.5%, that associated with a high specific sediment yield, will cause its full silting in at most 57 years. It is recommended to minimize this process the restoration of permanent preservation areas and the removal of 17,500 m³ of sediment from the riverbed of the dam.

O uso e a ocupação dos solos exercem influência marcante no escoamento superficial e aporte de sedimentos no leito dos mananciais, podendo alterar a qualidade e a disponibilidade da água. Com isto se objetivou com o presente trabalho, verificar a influência do uso e ocupação dos solos sobre os recursos hídricos do córrego Três Barras, município de Marinópolis, SP. Para constatar esta influência, realizou-se uma análise de correlação de Pearson entre os parâmetros de qualidade e disponibilidade de água e o uso e ocupação dos solos, cujos dados foram coletados entre 18/01/2006 a 10/12/2007. Concluiu-se que as áreas ocupadas por matas e pastagens (com menor intensidade) favoreceram a disponibilidade e a qualidade da água na Sub-Bacia. De maneira geral, as áreas habitadas, agricultadas e as matas degradadas, reduziram a disponibilidade e a qualidade da água da Sub-Bacia.

Land occupation and its use have a remarkable influence on the superficial water flow and the carrying of sediments to the riverbed and may change the quality and availability of water. The current study aimed to check the influence of the land occupation and use on the Três Barras stream resources, in Marinópolis, SP, Brazil. To check this influence, an analysis of Pearson's correlation between the parameters of quality and availability and use of water and land was developed. The samples covered the period of January, 2006 until December, 2007. It may be concluded that areas occupied by forests and pastures (in less intensity) favoured the availability and quality of water of the watershed. The inhabited areas and those used for agriculture, and the degraded forests in general, reduced the availability and quality of water in the watershed.