In looking at your db, I see several things that I would call issues.
In tables "tbl_RiffleData" and "tbl_DischargeDetail", it looks like they are linked in a 1-to-1 relationship. And they have a compound Primary Key. Then two field involved with the compound PK are text type fields.
Looking at the SQL of the query "qsel_edit_DischargeDetail", there are two columns are for "Notes". While this does not hurt anything, I would delete one column.
Code:
SELECT tbl_DischargeDetail.Season, tbl_DischargeDetail.LocationID, tbl_DischargeDetail.EventID, tbl_DischargeDetail.DischargeNo, tbl_DischargeDetail.DistanceFromBank_m,
tbl_DischargeDetail.Depth_cm, tbl_DischargeDetail.Notes, tbl_DischargeDetail.Notes AS Expr1, tbl_DischargeDetail.Units, tbl_DischargeDetail.DETimeStamp, tbl_Locations.ParkCode
FROM tbl_Locations INNER JOIN tbl_DischargeDetail ON (tbl_Locations.LocationID = tbl_DischargeDetail.LocationID) AND (tbl_Locations.LocationID = tbl_DischargeDetail.LocationID)
WHERE (((tbl_DischargeDetail.Season)=2007) AND ((tbl_Locations.ParkCode)="BUFF"))
ORDER BY tbl_DischargeDetail.Season, tbl_DischargeDetail.LocationID, tbl_DischargeDetail.EventID, tbl_DischargeDetail.DischargeNo;
Look at the FROM clause... don't know how you did this, but it doesn't look correct.
If you delete the RED part , the query becomes editable (at least for me).
Microsoft Access Tables: Primary Key Tips and Techniques