e. lower flow percentiles), and the coefficients associated to the perimeter tend to decrease for lower flow metrics (i.e. higher flow percentiles). These behaviors could reflect the influence of the wetted areas and the water head on seepage rates during flood events and the influence of evaporation and seepage combined to the flow transit time across the catchment during low flow periods. These suppositions

need to be strengthened by further research on this topic. The drainage density quantifies the level of catchment drainage by stream channels. Lower drainage density corresponds to flatter land with less differentiated drainage paths. High values imply steeper-sided selleck screening library thalweg, shorter flow transfer time and a sharper hydrograph. As would be anticipated, the coefficients of the drainage density are consistently positive and negative for high flow and low flow, respectively. Flow percentiles of intermediate magnitude are not influenced by the drainage density (Table 3). The surface ratio of paddy rice is negatively correlated to four low-flow variables (0.60, 0.70, 0.80 and 0.95). One possible explanation is the ability of paddy fields to reduce groundwater recharge due to the impermeable soil layer below the rice root zone, which contributes to the maintenance of ponded water in the bunded rice fields and increased evapotranspiration AZD5363 (Bouman et al., 2007). The signs of the coefficients associated to the other

explanatory variables are more difficult to explain. For instance, the positive coefficients relating to slope, for extreme high and low flows metrics only (Table 3) are difficult to interpret, corroborating the acknowledged complexity of the relationship between infiltration rate PtdIns(3,4)P2 and slope steepness (Ribolzi et al., 2011). It is also difficult to interpret the majority of positive coefficients associated to the mean elevation. Strikingly, latitude is negatively correlated to virtually all low

flow variables above the 0.50 percentile. It is tempting to conclude that latitude is a surrogate for an environmental variable controlling flow production, not listed in Table 2, and exhibiting a latitudinal gradient. However, at this stage, it is not possible to provide a candidate explanation for this particular behavior. The nature of the causal link between increased forest coverage and greater median flow (50%) (cf. the positive coefficient in Table 3) is also questionable and could be interpreted in many ways. Given the complex relationship between tropical forest and hydrology (Bruijnzeel, 2004), it is wiser not to provide a physical explanation without further research. Table 3 shows that Radj2 and Rpred2 values are excellent (>90%) for most of the variables. According to the t  -ratio values reported in Table 3, the predictors with the greatest explanatory power are “drainage area” or “perimeter”, depending on the predicted flow metrics.