Modeling the impact of invasive vegetation on stream flow in the Hamakua Coast
Ayron M. Strauch, Univ. of Hawai’i at ManoaRich MacKenzie, Greg Bruland, Christian Giardina,
Chris Heider, Ed Salminen, Tara Holitzki
Using a precipitation gradient to understand climate change
Plant invasions can also impact hydrology and aquatic ecosystems
Establishing long-term study sites
Long-term monitoring
•Establishes a baseline dataset•Examine inter-annual variations in stream flow•Helps to validate our model
Remote Sensing and Model Development: DHSVM
• Data driven- recreate “reality”– Climate, Hydrology, Soils, Vegetation, other data
• Compare “reality” with actuality at specific points and actual events on the landscape (gages)
• Run Scenarios and Compare Effects
• 157 Watersheds• Climate• Stream flow• Soil• Vegetation
DHSVM: using station data to model hydrology
*Current model uses parameters developed for global applications...not very specific to Hawai’ian conditions
Reality Check: Validation
• Modeled Flow vs Gauge Observation • 97% Agreement in Total Water Balance
Site 90: N. Laupāhoehoe
YELLOW: Existing invasive species types
RED: 300 m expansion areas
Scenario I: Invasive Species – Laupāhoehoe River
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec-30%
-25%
-20%
-15%
-10%
-5%
0%
5%
Average 5-10% less water
Certain years >20% reduction in flows
% c
han
ge in m
onth
ly fl
ow
Moving forward, developing partnerships
•integrate research across forest and aquatic ecosystems to examine how climate change and invasive species impact watersheds at the landscape scale
•coordinate research amongst various state, federal and NGO’s
•provide knowledge and tools to address impacts from climate change and invasive strawberry guava
Future work• continue to improve the DHSVM as well as run the model under different climate scenarios
• initiate stream sampling/monitoring over the next four years
• set up field experiments to determine how invasive species are impacting sediment loads and hydrology of streams
• establish downstream study sites that will include ecological parameters of native gobies (o`opu) and shrimp (opae)
Greg Bruland, Rich MacKenzie, Christian Giardina, Topaz Collins, Ka`eo Duarte, Tom Giamballuca,, Chris Heider, Tara Holitzki, Caitlin Kryss, Imiola Lindsey, Jamie Wong, Tom Schmidt, Keali’i Sagum
Research was/is funded by NSF REAP, PRISM, and the USDA FS
Feral pigs may also be influencing hydrology
Pig erosion Pig exclusion
