diff --git a/DESCRIPTION b/DESCRIPTION
index 80f80524c827e463cb01845bdff60587c3d9abc4..7e31d1d1799e14424ac95e02484b6bd18e2a2cf1 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,8 +1,8 @@
 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.6.3.23
-Date: 2020-10-27
+Version: 1.6.3.30
+Date: 2020-11-06
 Authors@R: c(
   person("Laurent", "Coron", role = c("aut", "trl"), comment = c(ORCID = "0000-0002-1503-6204")),
   person("Olivier", "Delaigue", role = c("aut", "cre"), comment = c(ORCID = "0000-0002-7668-8468"), email = "airGR@inrae.fr"),
diff --git a/NEWS.md b/NEWS.md
index 99ffdce14356d1acf14024502452e02172e763c7..f55f3c6a3e808bbab4bc8a4740e69150b8416b20 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,7 +4,7 @@
 
 
 
-### 1.6.3.23 Release Notes (2020-10-27)
+### 1.6.3.30 Release Notes (2020-11-06)
 
 #### New features
 
@@ -20,6 +20,11 @@
 - The deprecated <code>RunSnowModule</code> argument has been removed from the <code>CreateRunOptions()</code> function. ([#23](https://gitlab.irstea.fr/HYCAR-Hydro/airgr/-/issues/23))
 
 
+#### Bug fixes
+
+- Fixed bug in <code>RunModel_GR1A()</code>. Reversed PotEvap and Precip outputs are now reordered (in the previous versions PotEvap contained the precipitation values and Precip contained the evapotranspiration values, the Qsim values were already correct).
+
+
 #### Major user-visible changes
 
 - Added output to <code>RunModel_GR2M()</code> function (Ps). ([#51](https://gitlab.irstea.fr/HYCAR-Hydro/airgr/-/issues/51))
@@ -31,6 +36,7 @@
 
 #### Minor user-visible changes
 
+- <code>RunModel_GR1A()</code> now uses the Fortran version of the model code. This code is no longer duplicated: the R version which was used is removed.
 - Character argument verification now use partial matching in <code>PE_Oudin()</code> and <code>SeriesAggreg()</code> functions. ([#37](https://gitlab.irstea.fr/HYCAR-Hydro/airgr/-/issues/37))
 
 
diff --git a/R/RunModel_GR1A.R b/R/RunModel_GR1A.R
index d636ab4d2ab7e04e73a47d6334965c1614c563ef..432a1eaa9e22c1a51ef9c97faffd7e82298c6730 100644
--- a/R/RunModel_GR1A.R
+++ b/R/RunModel_GR1A.R
@@ -1,91 +1,103 @@
-RunModel_GR1A <- function(InputsModel,RunOptions,Param){
-
-    NParam <- 1;
-    FortranOutputs <- .FortranOutputs(GR = "GR1A")$GR
-
-    ##Arguments_check
-      if(inherits(InputsModel,"InputsModel")==FALSE){ stop("'InputsModel' must be of class 'InputsModel'") }  
-      if(inherits(InputsModel,"yearly"     )==FALSE){ stop("'InputsModel' must be of class 'yearly'     ") }  
-      if(inherits(InputsModel,"GR"         )==FALSE){ stop("'InputsModel' must be of class 'GR'         ") }  
-      if(inherits(RunOptions,"RunOptions"  )==FALSE){ stop("'RunOptions' must be of class 'RunOptions'  ") }  
-      if(inherits(RunOptions,"GR"          )==FALSE){ stop("'RunOptions' must be of class 'GR'          ") }  
-      if(!is.vector(Param) | !is.numeric(Param)){ stop("'Param' must be a numeric vector") }
-      if(sum(!is.na(Param))!=NParam){ stop(paste("'Param' must be a vector of length ",NParam," and contain no NA",sep="")) }
-      Param <- as.double(Param);
-
-    ##Input_data_preparation
-      if(identical(RunOptions$IndPeriod_WarmUp,as.integer(0))){ RunOptions$IndPeriod_WarmUp <- NULL; }
-      IndPeriod1   <- c(RunOptions$IndPeriod_WarmUp,RunOptions$IndPeriod_Run);
-      LInputSeries <- as.integer(length(IndPeriod1))
-      if("all" %in% RunOptions$Outputs_Sim){ IndOutputs <- as.integer(1:length(FortranOutputs)); 
-      } else { IndOutputs <- which(FortranOutputs %in% RunOptions$Outputs_Sim);  }
-
-    ##Output_data_preparation
-      IndPeriod2     <- (length(RunOptions$IndPeriod_WarmUp)+1):LInputSeries;
-      ExportDatesR   <- "DatesR"   %in% RunOptions$Outputs_Sim;
-      ExportStateEnd <- "StateEnd" %in% RunOptions$Outputs_Sim;
-    
-    BOOL_Fortran <- FALSE; if(BOOL_Fortran){
-    ##Call_fortan
-      RESULTS <- .Fortran("frun_gr1a",PACKAGE="airGR",
-                 ##inputs
-                     LInputs=LInputSeries,                             ### length of input and output series
-                     InputsPrecip=InputsModel$Precip[IndPeriod1],      ### input series of total precipitation [mm/y]
-                     InputsPE=InputsModel$PotEvap[IndPeriod1],         ### input series potential evapotranspiration [mm/y]
-                     NParam=as.integer(length(Param)),                 ### number of model parameter
-                     Param=Param,                                      ### parameter set
-                     NStates=as.integer(length(RunOptions$IniStates)), ### number of state variables used for model initialising
-                     StateStart=RunOptions$IniStates,                  ### state variables used when the model run starts
-                     NOutputs=as.integer(length(IndOutputs)),          ### number of output series
-                     IndOutputs=IndOutputs,                            ### indices of output series
-                 ##outputs
-                     Outputs=matrix(as.double(-999.999),nrow=LInputSeries,ncol=length(IndOutputs)),  ### output series [mm]
-                     StateEnd=rep(as.double(-999.999),length(RunOptions$IniStates))                  ### state variables at the end of the model run
-                     )
-      RESULTS$Outputs[ round(RESULTS$Outputs ,3)==(-999.999)] <- NA;
-      RESULTS$StateEnd[round(RESULTS$StateEnd,3)==(-999.999)] <- NA;
-
-    } else {
-    ##R_version
-      L  <- length(IndPeriod1)
-      P0 <- InputsModel$Precip[ IndPeriod1][1:(L-1)]
-      P1 <- InputsModel$Precip[ IndPeriod1][2: L   ]
-      E1 <- InputsModel$PotEvap[IndPeriod1][2: L   ]
-      Q1 <- P1*(1.-1./(1.+((0.7*P1+0.3*P0)/Param[1]/E1)^2.0)^0.5)
-      PEQ <- rbind(c(NA,NA,NA),cbind(P1,E1,Q1))
-      Outputs <- PEQ[,IndOutputs]
-      if(is.vector(Outputs)){ Outputs <- cbind(Outputs); }
-      RESULTS <- list(NOutputs=length(IndOutputs),IndOutputs=IndOutputs,Outputs=Outputs,StatesEnd=NA)
-   }
-        
-    
-    ##Output_data_preparation
-      ##OutputsModel_only
-      if(ExportDatesR==FALSE & ExportStateEnd==FALSE){
-        OutputsModel <- lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2,i]);
-        names(OutputsModel) <- FortranOutputs[IndOutputs];      }
-      ##DatesR_and_OutputsModel_only
-      if(ExportDatesR==TRUE & ExportStateEnd==FALSE){
-        OutputsModel <- c( list(InputsModel$DatesR[RunOptions$IndPeriod_Run]),
-                           lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2,i]) );
-        names(OutputsModel) <- c("DatesR",FortranOutputs[IndOutputs]);      }
-      ##OutputsModel_and_SateEnd_only
-      if(ExportDatesR==FALSE & ExportStateEnd==TRUE){
-        OutputsModel <- c( lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2,i]),
-                           list(RESULTS$StateEnd) );
-        names(OutputsModel) <- c(FortranOutputs[IndOutputs],"StateEnd");      }
-      ##DatesR_and_OutputsModel_and_SateEnd
-      if((ExportDatesR==TRUE & ExportStateEnd==TRUE) | "all" %in% RunOptions$Outputs_Sim){
-        OutputsModel <- c( list(InputsModel$DatesR[RunOptions$IndPeriod_Run]),
-                           lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2,i]),
-                           list(RESULTS$StateEnd) );
-        names(OutputsModel) <- c("DatesR",FortranOutputs[IndOutputs],"StateEnd");      }
-
-
-    ##End
-      rm(RESULTS); 
-      class(OutputsModel) <- c("OutputsModel","yearly","GR");
-      return(OutputsModel);
-
+RunModel_GR1A <- function(InputsModel, RunOptions, Param) {
+  
+  NParam <- 1
+  FortranOutputs <- .FortranOutputs(GR = "GR1A")$GR
+  
+  
+  ## Arguments_check
+  if (!inherits(InputsModel, "InputsModel")) {
+    stop("'InputsModel' must be of class 'InputsModel'")
+  }
+  if (!inherits(InputsModel, "yearly")) {
+    stop("'InputsModel' must be of class 'yearly'")
+  }
+  if (!inherits(InputsModel, "GR")) {
+    stop("'InputsModel' must be of class 'GR'")
+  }
+  if (!inherits(RunOptions, "RunOptions")) {
+    stop("'RunOptions' must be of class 'RunOptions'")
+  }
+  if (!inherits(RunOptions, "GR")) {
+    stop("'RunOptions' must be of class 'GR'")
+  }
+  if (!is.vector(Param) | !is.numeric(Param)) {
+    stop("'Param' must be a numeric vector")
+  }
+  if (sum(!is.na(Param)) != NParam) {
+    stop(paste("'Param' must be a vector of length", NParam, "and contain no NA"))
+  }
+  Param <- as.double(Param)
+  
+  
+  ## Input data preparation
+  if (identical(RunOptions$IndPeriod_WarmUp, 0L)) {
+    RunOptions$IndPeriod_WarmUp <- NULL
+  }
+  IndPeriod1 <- c(RunOptions$IndPeriod_WarmUp, RunOptions$IndPeriod_Run)
+  LInputSeries <- as.integer(length(IndPeriod1))
+  if ("all" %in% RunOptions$Outputs_Sim) {
+    IndOutputs <- as.integer(1:length(FortranOutputs))
+  } else {
+    IndOutputs <- which(FortranOutputs %in% RunOptions$Outputs_Sim)
+  }
+  
+  
+  ## Output data preparation
+  IndPeriod2     <- (length(RunOptions$IndPeriod_WarmUp) + 1):LInputSeries
+  ExportDatesR   <- "DatesR"   %in% RunOptions$Outputs_Sim
+  ExportStateEnd <- "StateEnd" %in% RunOptions$Outputs_Sim
+  
+  
+  ## Call_fortan
+  RESULTS <- .Fortran("frun_gr1a", PACKAGE = "airGR",
+                      ## inputs
+                      LInputs = LInputSeries,                             ### length of input and output series
+                      InputsPrecip = InputsModel$Precip[IndPeriod1],      ### input series of total precipitation [mm/y]
+                      InputsPE = InputsModel$PotEvap[IndPeriod1],         ### input series potential evapotranspiration [mm/y]
+                      NParam = as.integer(length(Param)),                 ### number of model parameter
+                      Param = Param,                                      ### parameter set
+                      NStates = as.integer(length(RunOptions$IniStates)), ### number of state variables used for model initialising
+                      StateStart = RunOptions$IniStates,                  ### state variables used when the model run starts
+                      NOutputs = as.integer(length(IndOutputs)),          ### number of output series
+                      IndOutputs = IndOutputs,                            ### indices of output series
+                      ## outputs
+                      Outputs = matrix(as.double(-999.999), nrow = LInputSeries,ncol=length(IndOutputs)), ### output series [mm]
+                      StateEnd = rep(as.double(-999.999), length(RunOptions$IniStates))                   ### state variables at the end of the model run
+  )
+  RESULTS$Outputs[ round(RESULTS$Outputs , 3) == (-999.999)] <- NA
+  RESULTS$StateEnd[round(RESULTS$StateEnd, 3) == (-999.999)] <- NA
+  
+  
+  ## Output data preparation
+  ## OutputsModel only
+  if (!ExportDatesR & !ExportStateEnd) {
+    OutputsModel <- lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2, i])
+    names(OutputsModel) <- FortranOutputs[IndOutputs]
+  }
+  ## DatesR and OutputsModel only
+  if (ExportDatesR & !ExportStateEnd) {
+    OutputsModel <- c(list(InputsModel$DatesR[RunOptions$IndPeriod_Run]),
+                      lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2, i]))
+    names(OutputsModel) <- c("DatesR", FortranOutputs[IndOutputs])
+  }
+  ## OutputsModel and SateEnd only
+  if (!ExportDatesR & ExportStateEnd) {
+    OutputsModel <- c(lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2, i]),
+                      list(RESULTS$StateEnd))
+    names(OutputsModel) <- c(FortranOutputs[IndOutputs], "StateEnd")
+  }
+  ## DatesR and OutputsModel and SateEnd
+  if ((ExportDatesR & ExportStateEnd) | "all" %in% RunOptions$Outputs_Sim) {
+    OutputsModel <- c(list(InputsModel$DatesR[RunOptions$IndPeriod_Run]),
+                      lapply(seq_len(RESULTS$NOutputs), function(i) RESULTS$Outputs[IndPeriod2, i]),
+                      list(RESULTS$StateEnd))
+    names(OutputsModel) <- c("DatesR", FortranOutputs[IndOutputs], "StateEnd")
+  }
+  
+  
+  ## End
+  class(OutputsModel) <- c("OutputsModel", "yearly", "GR")
+  return(OutputsModel)
+  
 }