Watershed Analysis - Teaching Notes and Tips

Common Trouble Spots

• A student doesn't have a good grasp of geography (and place names) of their chosen area.
• Solution: have them work with maps from the area(e.g. Google Maps: http://maps.google.com/).
• No precipitation stations are located within the watershed of choice.
• Solution: have them use a precipitation station within a nearby watershed (but on same side of mountain range to ensure conditions similar to their watershed).
• The chosen precipitation station is at the same (or lower) elevation as the discharge station. This results in more water reported exiting than entering the catchment.
• Solution: Either have them redo the part of the assignment, or discuss the influence of the orographic effect on their results.
• Unit conversion. The most common error seems to occur in the conversion from daily discharge measurements (reported in cubic feet per second, cfs) to annual discharge (cubic feet per year, cfy).
• Solution: Students are usually comfortable converting the daily measurements in cfs to cfd (cubic feet per day). However, going from cfd to cfy presents the problem. Summing the daily numbers yields the total discharge for the year (cfy). The problem: students will often sum the data then convert days to years, resulting in a discharge value more than 300X too large.