v1.6.2.2 feat: limit negative flow in SD model

- if direct upstream flow leads to negative downstream flow a warning is displayed and downstream flow is set to zero

Refs #34

DESCRIPTION

 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.6.2.1
+Version: 1.6.2.2
 Date: 2020-06-05
 Authors@R: c(
   person("Laurent", "Coron", role = c("aut", "trl"), comment = c(ORCID = "0000-0002-1503-6204")),

R/RunModel.R

@@ -36,6 +36,11 @@ RunModel <- function (InputsModel, RunOptions, Param, FUN_MOD) {
           Qupstream[(2 + floor(PT[upstream_basin])):LengthTs]) *
         HUTRANS[2, upstream_basin]
     }
+    # Warning for negative flows
+    if(any(OutputsModelDown$Qsim < 0)) {
+      warning(length(which(OutputsModelDown$Qsim < 0)), " time steps with negative flow, set to zero.")
+      OutputsModelDown$Qsim[OutputsModelDown$Qsim < 0] <- 0
+    }
     # Convert back Qsim to mm
     OutputsModelDown$Qsim <- OutputsModelDown$Qsim / sum(InputsModel$BasinAreas, na.rm = TRUE) / 1E3