manoa stream at manoa district park

Station MRC

Looking up Manoa Stream from our Station MRC located at Manoa District Park.  We do not have a monitoring system at this station, however, we manually sample at this location on a quarterly basis and occasionally during storms.  In addition to water quality data, we also measure instantaneous stream flow with a current meter (see photos below).  Notice that the stream has been modified at this location.

Looking down Manoa Stream from Station MRC.  Again, note that the stream has been modified.  Modifications include channelization of the stream with either vegetation, rock, or concrete lining of the channel.  In a natural stream, the bends or meanders in the stream and the vegetation all serve to remove pollutants introduced to the stream during storms.  The modifications seen in these photos increase the amount of pollutants that eventually reach the sea.

Looking under the Kahaloa Drive Bridge up toward the weir located on Manoa Stream at Station MRC.  Weirs and concrete channel bottoms represent other types of modifications that have been made to Manoa Stream.  These modifications often lead to excessive heating of stream waters due to insolation (solar heating).  Elevated temperatures can have deleterious effects on stream biota.

A number of storm drains enter Manoa Stream at this location.  Three of these drains are shown in this photo taken under the bridge.  Most of these drains direct stormwater into the stream from the roads.  This stormwater is often laden with pollutants such as oils (lubricants and fuels), metals (tires and break linings), and organic material with high biochemical oxygen demand (BOD).

More storm drains immediately downstream (and on the opposite side) of those shown above.  Even if the drains do not drain streets, they still represent potential sources of pollutants in the form of nutrients (from fertilizers) and fecal bacteria (from pets and other animals).