Index: /issm/trunk-jpl/src/c/classes/Loads/Friction.cpp
===================================================================
--- /issm/trunk-jpl/src/c/classes/Loads/Friction.cpp	(revision 22848)
+++ /issm/trunk-jpl/src/c/classes/Loads/Friction.cpp	(revision 22849)
@@ -670,14 +670,12 @@
 	*palpha2=alpha2;
 }/*}}}*/
+
 IssmDouble Friction::EffectivePressure(Gauss* gauss){/*{{{*/
-	/*Get effective pressure as a function of 
-	 *  - coupling
-	 *  - type
-	 * Neff=rho_ice*g*thickness+rho_ice*g*base
-	 */
-
+	/*Get effective pressure as a function of  flag */
 
 	/*diverse: */
 	int         coupled_flag;
+	IssmDouble  thickness,base,sealevel;
+	IssmDouble  p_ice,p_water;
 	IssmDouble  Neff;
 
@@ -688,18 +686,40 @@
 	switch(coupled_flag){
 		case 0:{
-		   IssmDouble  thickness,base,sealevel;
-			element->GetInputValue(&thickness, gauss,ThicknessEnum);
-			element->GetInputValue(&base, gauss,BaseEnum);
-			element->GetInputValue(&sealevel, gauss,SealevelEnum);
-			IssmDouble rho_water = element->GetMaterialParameter(MaterialsRhoSeawaterEnum);
-			IssmDouble rho_ice   = element->GetMaterialParameter(MaterialsRhoIceEnum);
-			IssmDouble gravity   = element->GetMaterialParameter(ConstantsGEnum);
-			Neff=gravity*(rho_ice*thickness+rho_water*(base-sealevel));
+					 element->GetInputValue(&thickness, gauss,ThicknessEnum);
+					 IssmDouble rho_ice   = element->GetMaterialParameter(MaterialsRhoIceEnum);
+					 IssmDouble gravity   = element->GetMaterialParameter(ConstantsGEnum);
+					 p_ice   = gravity*rho_ice*thickness;
+					 p_water = 0.;
+					 Neff = p_ice - p_water;
 				 }
-			break;
-		case 1:
+			  break;
+		case 1:{
+					 element->GetInputValue(&thickness, gauss,ThicknessEnum);
+					 element->GetInputValue(&base, gauss,BaseEnum);
+					 element->GetInputValue(&sealevel, gauss,SealevelEnum);
+					 IssmDouble rho_water = element->GetMaterialParameter(MaterialsRhoSeawaterEnum);
+					 IssmDouble rho_ice   = element->GetMaterialParameter(MaterialsRhoIceEnum);
+					 IssmDouble gravity   = element->GetMaterialParameter(ConstantsGEnum);
+					 p_ice   = gravity*rho_ice*thickness;
+					 p_water = max(0.,rho_water*gravity*(sealevel-base));
+					 Neff = p_ice - p_water;
+				 }
+			  break;
+		case 2:{
+					 element->GetInputValue(&thickness, gauss,ThicknessEnum);
+					 element->GetInputValue(&base, gauss,BaseEnum);
+					 element->GetInputValue(&sealevel, gauss,SealevelEnum);
+					 IssmDouble rho_water = element->GetMaterialParameter(MaterialsRhoSeawaterEnum);
+					 IssmDouble rho_ice   = element->GetMaterialParameter(MaterialsRhoIceEnum);
+					 IssmDouble gravity   = element->GetMaterialParameter(ConstantsGEnum);
+					 p_ice   = gravity*rho_ice*thickness;
+					 p_water = rho_water*gravity*(sealevel-base);
+					 Neff = p_ice - p_water;
+				 }
+			  break;
+		case 3:
 			element->GetInputValue(&Neff,gauss,FrictionEffectivePressureEnum);
 			break;
-		case 2:
+		case 4:
 			element->GetInputValue(&Neff,gauss,EffectivePressureTimeAverageEnum);
 			break;
Index: /issm/trunk-jpl/src/m/classes/friction.m
===================================================================
--- /issm/trunk-jpl/src/m/classes/friction.m	(revision 22848)
+++ /issm/trunk-jpl/src/m/classes/friction.m	(revision 22849)
@@ -20,6 +20,8 @@
 				case 0
 				case 1
+				case 2
+				case 3
 					self.effective_pressure=project3d(md,'vector',self.effective_pressure,'type','node','layer',1);
-				case 2
+				case 4
 					error('not implemented yet');
 				otherwise
@@ -39,4 +41,6 @@
 		function self = setdefaultparameters(self) % {{{
 
+			self.coupling = 0;
+
 		end % }}}
 		function md = checkconsistency(self,md,solution,analyses) % {{{
@@ -49,10 +53,12 @@
 			md = checkfield(md,'fieldname','friction.q','NaN',1,'Inf',1,'size',[md.mesh.numberofelements 1]);
 			md = checkfield(md,'fieldname','friction.p','NaN',1,'Inf',1,'size',[md.mesh.numberofelements 1]);
-			md = checkfield(md,'fieldname','friction.coupling','numel',[1],'values',[0 1 2]);
+			md = checkfield(md,'fieldname','friction.coupling','numel',[1],'values',[0:4]);
 			switch self.coupling
 				case 0
 				case 1
+				case 2
+				case 3
 					md = checkfield(md,'fieldname','friction.effective_pressure','NaN',1,'Inf',1,'timeseries',1);
-				case 2
+				case 4
 					error('not implemented yet');
 				otherwise
@@ -66,5 +72,5 @@
 			fielddisplay(self,'q','q exponent');
 			fielddisplay(self,'effective_pressure','Effective Pressure for the forcing if not coupled [Pa]');
-			fielddisplay(self,'coupling','Coupling flag: 0 for default, 1 for forcing(provide md.friction.effective_pressure)  and 2 for coupled(not implemented yet)');
+			fielddisplay(self,'coupling','Coupling flag 0: uniform sheet (negative pressure ok, default), 1: ice pressure only, 2: water pressure assuming uniform sheet (no negative pressure), 3: use provided effective_pressure, 4: used coupled model (not implemented yet)');
 		end % }}}
 		function marshall(self,prefix,md,fid) % {{{
Index: /issm/trunk-jpl/src/m/classes/friction.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/friction.py	(revision 22848)
+++ /issm/trunk-jpl/src/m/classes/friction.py	(revision 22849)
@@ -29,5 +29,5 @@
 		string="%s\n%s"%(string,fielddisplay(self,"p","p exponent"))
 		string="%s\n%s"%(string,fielddisplay(self,"q","q exponent"))
-		string="%s\n%s"%(string,fielddisplay(self,'coupling','Coupling flag: 0 for default, 1 for forcing(provide md.friction.effective_pressure)  and 2 for coupled(not implemented yet)'))
+                string="%s\n%s"%(string,fielddisplay(self,'coupling','Coupling flag 0: uniform sheet (negative pressure ok, default), 1: ice pressure only, 2: water pressure assuming uniform sheet (no negative pressure), 3: use provided effective_pressure, 4: used coupled model (not implemented yet)'))
 		string="%s\n%s"%(string,fielddisplay(self,'effective_pressure','Effective Pressure for the forcing if not coupled [Pa]'))
 		return string
@@ -38,10 +38,10 @@
 		self.q=project3d(md,'vector',self.q,'type','element')
 		#if self.coupling==0: #doesnt work with empty loop, so just skip it?
-		if self.coupling==1:
+		if self.coupling==3:
 			self.effective_pressure=project3d(md,'vector',self.effective_pressure,'type','node','layer',1)
-		elif self.coupling==2:
+		elif self.coupling==4:
 			raise ValueError('coupling not supported yet')
-		elif self.coupling > 2:
-			raise ValueError('md.friction.coupling larger than 2, not supported yet')
+		elif self.coupling > 4:
+			raise ValueError('md.friction.coupling larger than 4, not supported yet')
 		return self
 	#}}}
@@ -58,9 +58,9 @@
 		md = checkfield(md,'fieldname','friction.q','NaN',1,'Inf',1,'size',[md.mesh.numberofelements])
 		md = checkfield(md,'fieldname','friction.p','NaN',1,'Inf',1,'size',[md.mesh.numberofelements])
-		md = checkfield(md,'fieldname','friction.coupling','numel',[1],'values',[0,1,2])
-		if self.coupling==1:
+		md = checkfield(md,'fieldname','friction.coupling','numel',[1],'values',[0,1,2,3,4])
+		if self.coupling==3:
 			md = checkfield(md,'fieldname','friction.effective_pressure','NaN',1,'Inf',1,'timeseries',1)
-		elif self.coupling > 2:
-			raise ValueError('md.friction.coupling larger than 2, not supported yet')
+		elif self.coupling > 4:
+			raise ValueError('md.friction.coupling larger than 4, not supported yet')
 		return md
 	# }}}
@@ -71,7 +71,7 @@
 		WriteData(fid,prefix,'object',self,'fieldname','q','format','DoubleMat','mattype',2)
 		WriteData(fid,prefix,'class','friction','object',self,'fieldname','coupling','format','Integer')
-		if self.coupling==1:
+		if self.coupling==3:
 			WriteData(fid,prefix,'class','friction','object',self,'fieldname','effective_pressure','format','DoubleMat','mattype',1,'timeserieslength',md.mesh.numberofvertices+1,'yts',md.constants.yts)
-		elif self.coupling > 2:
+		elif self.coupling > 4:
 			raise ValueError('md.friction.coupling larger than 2, not supported yet')
 	# }}}