diff --git a/src/MNH/shallow_mf_pack.f90 b/src/MNH/shallow_mf_pack.f90
index 421a54d6b3598337e2c498090c7bedbd62f2d385..a91a1d9722befa1e1af18c90a00d0707c8783ca8 100644
--- a/src/MNH/shallow_mf_pack.f90
+++ b/src/MNH/shallow_mf_pack.f90
@@ -114,6 +114,7 @@ END MODULE MODI_SHALLOW_MF_PACK
 !!      V.Masson 09/2010
 !!      Modification R. Honnert 07/2012 : introduction of vertical wind 
 !!                                        for the height of the thermal
+!!                   M. Leriche 02/2017 : avoid negative values for sv tendencies
 !! --------------------------------------------------------------------------
 !
 !*      0. DECLARATIONS
@@ -365,8 +366,8 @@ PRVS(:,:,:)   = PRVS(:,:,:)  +MYM(  &
 
 DO JSV=1,ISV 
   IF (LNOMIXLG .AND. JSV >= NSV_LGBEG .AND. JSV<= NSV_LGEND) CYCLE
-  PRSVS(:,:,:,JSV)   = PRSVS(:,:,:,JSV)  +    &
-                  PRHODJ(:,:,:)*ZDSVDT(:,:,:,JSV)
+  PRSVS(:,:,:,JSV)   = MAX((PRSVS(:,:,:,JSV)  +    &
+                  PRHODJ(:,:,:)*ZDSVDT(:,:,:,JSV)),XSVMIN(JSV))
 END DO     
 
 !!! 7. call to MesoNH budgets
diff --git a/src/MNH/turb_ver_sv_flux.f90 b/src/MNH/turb_ver_sv_flux.f90
index c3ec5d032a87c555859d442c25e112aae11d74f0..35aef367a7328d33656d5d733539d57819e2a331 100644
--- a/src/MNH/turb_ver_sv_flux.f90
+++ b/src/MNH/turb_ver_sv_flux.f90
@@ -267,6 +267,9 @@ END MODULE MODI_TURB_VER_SV_FLUX
 !!                                              change of YCOMMENT
 !!                     Feb 2012(Y. Seity) add possibility to run with reversed 
 !!                                              vertical levels
+!!                     Feb 2017(M. Leriche) add initialisation of ZSOURCE
+!!                                   to avoid unknwon values outside physical domain
+!!                                   and avoid negative values in sv tendencies
 !!--------------------------------------------------------------------------
 !       
 !*      0. DECLARATIONS
@@ -277,7 +280,7 @@ USE MODD_CTURB
 USE MODD_PARAMETERS
 USE MODD_LES
 USE MODD_CONF
-USE MODD_NSV, ONLY : NSV_LGBEG,NSV_LGEND
+USE MODD_NSV, ONLY : XSVMIN,NSV_LGBEG,NSV_LGEND
 !
 USE MODI_GRADIENT_U
 USE MODI_GRADIENT_V
@@ -397,6 +400,7 @@ DO JSV=1,ISV
   ZA(:,:,:)    = -PTSTEP*XCHF*PPSI_SV(:,:,:,JSV) *   &
                  ZKEFF * MZM(KKA,KKU,KKL,PRHODJ) /   &
                  PDZZ**2
+  ZSOURCE(:,:,:) = 0.
 !
 ! Compute the sources for the JSVth scalar variable
 
@@ -421,8 +425,8 @@ DO JSV=1,ISV
   CALL TRIDIAG(KKA,KKU,KKL,PSVM(:,:,:,JSV),ZA,PTSTEP,PEXPL,PIMPL,PRHODJ,ZSOURCE,ZRES)
 !
 !  Compute the equivalent tendency for the JSV scalar variable
-  PRSVS(:,:,:,JSV)= PRSVS(:,:,:,JSV)+    &
-                    PRHODJ(:,:,:)*(ZRES(:,:,:)-PSVM(:,:,:,JSV))/PTSTEP
+  PRSVS(:,:,:,JSV)= MAX((PRSVS(:,:,:,JSV)+    &
+                    PRHODJ(:,:,:)*(ZRES(:,:,:)-PSVM(:,:,:,JSV))/PTSTEP),XSVMIN(JSV))
 !
   IF ( (OTURB_FLX .AND. OCLOSE_OUT) .OR. LLES_CALL ) THEN
     ! Diagnostic of the cartesian vertical flux