The WAW initiative (World Agricultures Watch) intends to elaborate a worldwide observatory collecting information on agriculture in different countries and its evolution. Madagascar has been chosen as one of the pilot countries. The geographical area of the study which has been chosen is the lake Alaotra. The study of the notions of vulnerability, resilience, durability and viability has been the main point concerning the choice, the calculation and the analysis of the necessary indicators leading to the elaboration of the observatory. Three different data lines have been chosen: i) The database from the ROR, with annual data from 2005 to 2008 for 500 households ii) The database from the agricultural diagnosis BV-Lac in 2007 (110 farms) and iii) The database from RFR, with 48 farms in 2009 . This paper presents some results with farming systems modeling using the two databases from the BV-lac development project showing the indicators used through the example of a technical change with adoption of conservation agriculture.