diff --git a/srcF/module_z0t_lake.f90 b/srcF/module_z0t_lake.f90
index e73adb4950ba862e2aeb41dceca6ded4af758594..628d4db5ff409a75622575cd929dc08a44372d4e 100644
--- a/srcF/module_z0t_lake.f90
+++ b/srcF/module_z0t_lake.f90
@@ -138,10 +138,12 @@ module module_z0t_lake
        
       
        
-        ! --- define roughness [thermal]
-        z0_t = z0_m (-0.56*(4.0*sqtr(Re)-3.4))
+        
+        B=alog(-0.56*(4.0*(Re)**(0.5)-3.4))     !Repina, 2023
+
 
-        B=log(z0_m/z0_t)      !Repina, 2023
+       ! --- define roughness [thermal]
+        z0_t = z0_m / exp(B)   
        
     end subroutine