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In spite of the relative success of soil & water conservation programs in Brazil in the last 20 years, they have not explicitly considered their off-site benefits, or utilized compensation instruments. Considering these shortcomings, as well as the new trends in agri-environmental programs, the Brazilian National Water Agency-ANA developed a conservation and reclamation project aimed at strategic water supply sources, where the financial incentives for the participants are proportional to the off-site benefits provided, relative to the sedimentation abatement. Since the latter is not a trivial process, it was emulated by a simplified version of the Universal Soil Loss Equation-USLE, at the farm level. Thus, the financial incentives for the participant farmers were estimated as a function of the erosion and sedimentation abatement provided, as well as the cost of the adoption of the practice. The simplicity and robustness of the proposed method, as well as the ease of the certification process in the field, allow its decentralized implementation by watershed committees or cooperatives. The theoretical and methodological aspects of this project, entitled “Water Provider Program”, are presented in this paper. An example of the application of the method to a rural watershed in Brazil is presented in a companion paper, in this same issue (Chaves et al., 2004). APENDICE A A simplificacao proposta para a USLE, dada pela equacao [3] requer, no caso de introducao da pratica de terraceamento em nivel, uma demonstracao de que a reducao da erosao A, na equacao [2], e uma funcao linear da reducao do fator de comprimento de rampa, L. Na USLE, o fator L e definido como sendo (Wischmeier & Smith, 1978): L = ( l / 22,1)M [A1] Onde: l (m) = comprimento de rampa da gleba, e M = coeficiente proporcional a declividade da rampa (M varia entre 0,1 a 0,5). Como o terraceamento em nivel reduz o comprimento de rampa ( l ) mas nao a declividade da vertente, o valor de M na equacao [A1] nao e afetado. Assim, supondo que uma vertente agricola de area igual a 100 ha, com comprimento igual a l0=200m seja reduzida, com a introducao do terraceamento, a 4 vertentes iguais de l1=50 m (ou seja, l1= l0/4). Teremos assim a seguinte reducao relativa na perda de solo, A (t/ha ano): A1/A0 = L1/L0 = [( l1/22,1)M/( l0/22,1)M] [A2] = [(50/22,1)M (200/22,1)M] = 1⁄4 ou 25%, como queriamos demonstrar. Assim, no caso de terraceamento em nivel, um fator adicional (L) devera ser introduzido no fator consolidado Z, na estimativa de Z0 e Z1 para as equacoes [3] e [4]: Z = C*P*L [A3] Onde C e P foram definidos anteriormente.

Quantificação dos Benefícios Ambientais e Compensações Financeiras do ?Programa do Produtor de Água? (ANA): II. Aplicação