Abstract
The knowledge of the frequency and magnitude of low flow events is necessary to mitigate social, economic and ecological impacts inside the basin. However, the measurement network in Brazil is still restricted to large drainage areas, while basins with less than 300 km2 remain ungauged. Among different flow estimation methods, we used a rainfall-runoff model designed specifically to estimate flow rates during the dry season in small ungauged basins: the Silveira Method (SM). We tested the model performance for the São Bartolomeu river basin (Minas Gerais, Brazil), a small ungauged basin that experienced severe droughts and water supply shortages in 2014-2016. We tested eleven different scenarios based on the time and duration of drought periods used to estimate the model parameters. In the best scenario, the model underestimated low flow rates by 31% for Q95 and was considered suitable to predict local low flow. Finally, the model results suggest that a water volume higher than the river can support has been granted concession during the dry season, which may lead to an unsustainable water supply scenario soon. This result showed the capacity of SM as a complementary tool for the evaluation of water potential in small basins.
Highlights
The water availability in a catchment is commonly represented by median and low flows (Uliana et al 2016, Novaes et al 2009) and knowledge about its magnitude and frequency is necessary to mitigate social, economic and ecological impacts (Nicolle et al 2014, Grandry et al 2013, Novaes et al 2009)
Evaluation of the Silveira Method for planning water uses under water shortage conditions In order to evaluate the SM results for planning the water uses under shortage conditions, we considered the guidelines presented by the Deliberação Normativa do Conselho Estadual de Recursos Hídricos DN CERH/MG number 49/2015, which defines three possible levels of restrictions in scenarios of water scarcity (Minas Gerais 2015).The attention level occurs when the mean of the daily flows of seven consecutive days (Q7) is less than 200% of Q7,10
Eleven drought periods were considered for the application of SM: one for the Scenario 1.1, six for the Scenario 1.2 and four in Scenario 2
Summary
The water availability in a catchment is commonly represented by median and low flows (Uliana et al 2016, Novaes et al 2009) and knowledge about its magnitude and frequency is necessary to mitigate social, economic and ecological impacts (Nicolle et al 2014, Grandry et al 2013, Novaes et al 2009) These factors allow adequate planning and reduced conflict among multiple users of water resources (Pruski et al 2015, Novaes et al 2009). Flow estimation mechanisms have been widely used (Beskow et al 2013, Grandry et al 2013, WMO 2008), such as statistical methods, regional modelling, and rainfall-runoff models (Pruski et al 2015, GPRH, IGAM 2012)
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