Index: doc/faq.rst
===================================================================
diff -u -rb7f6c4b703a8f7f7bb1551a10f191d9404b34c1e -r21209c07f02e7264b5fa3ef2151b055a5deef29e
--- doc/faq.rst	(.../faq.rst)	(revision b7f6c4b703a8f7f7bb1551a10f191d9404b34c1e)
+++ doc/faq.rst	(.../faq.rst)	(revision 21209c07f02e7264b5fa3ef2151b055a5deef29e)
@@ -14,6 +14,8 @@
 
 [5]_ wflow complains about missing initial state maps
 
+[6]_ in some areas the mass balance error seems large
+
 Answers
 -------
 
@@ -52,3 +54,6 @@
 .. [5] *wflow complains about missing initial state maps*
     run the model with the -I option first and copy the resulting files in runid/outstate back to the instate directory
 
+.. [6] *in some areas the mass balance error seems large*
+   The simple explicit solution of most models can cuase this, especially when parameter values are outside
+   the nomally used range and with large timsteps. For example, setting the soil depth to zero will usually cuase large errors. The solution is usually to check the parameters throughout the model.
\ No newline at end of file