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Home My WebLink About02_Hydrologic-Stream-Classification-parts-1-&-2-Sam-Pearsall-and-Chris-GoudreauBACKGROUND AND PROGRESS TO DATE January 18, 2011 NC droughts 1998‐2002 and 2005‐2008 caused NC General Assembly to mandate a study of water management needs. 2008 Report of the Water Allocation Study of the NC Environmental Review Commission (Holman, Whisnant, et al.) Also Water Wiki: http://sogweb.sog.unc.edu/Water/ By winter 2008‐09 potential water law in development by multiple teams. DENR was already committed to developing hydrologic models for NC river basins. Structure and function of a riverine ecosystem, and the adaptations of its species/communities, are dictated by the temporal variation in a river’s flow regime. Variability of the flow regime determines species abundance and diversity, habitat availability, and drives disturbance and geomorphic processes. Magnitude, frequency, seasonal timing, duration and rate‐ of‐change of flow conditions are controlling aspects of the flow regime. Identify streams with similar hydrologic charac‐ teristics which, according to ecological theory, explain major aspects of their organization & structure ID unique hydro‐ecological indices that best describe (indices that make the class different from the other classes) the hydrologic variability of the stream class and stream reaches by addressing the six major components of flow ‐magnitude, frequency, duration, timing, rate of change, variability Allow for the development of class based flow/response relationships ecological flows EDF agreed to fund a classification study, if… DENR would help ensure the results were available to the public, and DENR and WRC would co‐supervise the study. John Heasley Jim Henriksen Station #Station Name Remarks in USGS Reports H D C N? W SP 2 4 0 3 ? PRELIM KEEP? USE IN UNALTERED DATASET LIMIT RECORD 03511000 OCONALUFTEE R @ CHEROKEE slight diurnal flux @ low flow fr u/s hydro Y Y Y 03512000 OCONALUFTEE R @ BIRDTOWN ok Y Y Y Y 03513000 TUCKASEGEE R @ BRYSON CITY regulated by u/s hydro reservoirs N N 03513500 NOLAND CK NR BRYSON CITY ok Y Y Y Y 03547000 HIWASSEE R BL CHATUGE NR HAYESVILLE completely regulated by TVA reservoir N N 03548500 HIWASSEE R AB MURPHY regulated since 1942 by TVA reservoir Y Y 1898 ‐1941 03550000 VALLEY R @ TOMOTLA ok Y Y Y Y 03554000 NOTTELY R NR RANGER regulated by TVA reservoir since 1/1942 Y Y Y 1902 ‐1941 0208732885 MARSH CK NR NEW HOPE ok Y Y 0208758850 SWIFT CK NR MCCULLARS CROSSROADS some regulation by Lake Wheeler u/s U Y 0208925200 BEAR CK @ MAYS STORE ok Y Y 0209741955 NORTHEAST CK @ SR1100 NR GENLEE wastewater diverted into basin u/s of gage U Y 0214253830 NORWOOD CK NR TROUTMAN ok Y Y 0344894205 N FK SWANNANOA R NR WALKERTOWN ok Y Y 0345577330 W FK PIGEON R NR RETREAT some low flow regulation by Lake Logan u/s Y Y 216 55 84 163 175 UNALTERED 35 33 ALTERED 18 8 UNSURE NC Stream Classification – Gages? Period of Record? 8 >= 18 Yrs POR 185 Gages 26 split POR 32 altered entire POR 2009 Environmental Flow Specialists, Inc. All Rights Reserved Classification was first developed using only unaltered gages Then a test classification was conducted including 46 gages with altered time periods. The results yielded the same number of classes (7) as the classification using only gages with unaltered time periods Furthermore, the altered gages did not fall into a separate class but several gages occurred in each of the unaltered classes. This was interpreted to mean that the altered gages are hydrologically similar to the unaltered classes and not distinctly different. Consequently, the classification proceeded using only gages with unaltered time periods. Flow Component Categories Number of Indices General Magnitude 8 Low Magnitude 13 High Magnitude 13 Frequency 12 Duration 6 Monthly Timing 14 Seasonal Timing 14 Rate of Change 4 Variability 17 Distribution of Annual Flow Among Six Flow States 7 = 108 Thepercentileranges forthesix flow statesare: Zero flow ‐state where no flow occurs. Very low flow ‐state where flow > 0 and <= 10 th percentile. Low flow ‐state where flow > 10 th and <= 25 th percentile. Average flow ‐state where flow > 25 th and <= 75 th percentile. High flow ‐state where flow > 75 th and <= 90 th percentile. Very High flow ‐state where flow > 90 th percentile. •22 variables were determined to be most deterministic. •They yielded 9 compound vectors. •In the space defined by these vectors, the gages clustered to define 7 classes characterized as the clusters with the smallest diameters and the largest distances between them. 162009 Environmental Flow Specialists, Inc. All Rights Reserved Presented to Ecological Flows Science Advisory Board January 18, 2011 Class Descriptions ‐Hydrologic 191/18/2011 SAB Presentation Class Characteristics – Hydrologic 201/18/2011 SAB Presentation Expert Workshop Experts 15 aquatic biologists, hydrologists and ecologists Objectives Do classes make sense hydrologically and ecologically Describe geomorphic and ecological characteristics of classes Adjust classes and class names, if appropriate Discuss strategies to use classes in developing ecological flows 211/18/2011 SAB Presentation Class Characteristics – General (Example) Class A –Coastal Streams Diadromous fish Winter and summer rains East of highway I‐95 High sinuosity Main channel connectivity to flood plain Black water (tannic) Snags are an important habitat feature Low gradient Stream bed material is fine particle size Salinity balance can be a factor, e.g. salt wedge location Channel maintenance flows important See DENR website for complete notes from workshop, including characteristics of all stream classes 221/18/2011 SAB Presentation Class A –Coastal Streams 231/18/2011 SAB Presentation Class B –Small Stable Streams 241/18/2011 SAB Presentation Class C –Large Stable Streams 251/18/2011 SAB Presentation Class D –Small Flashy Streams 261/18/2011 SAB Presentation Class E –Large Piedmont Rivers 271/18/2011 SAB Presentation Class F –Medium Stable Streams 281/18/2011 SAB Presentation Class G –Small Seasonal Streams 291/18/2011 SAB Presentation Further Revisions Workshop participants decided to subdivide two classes with wide geographic distribution (Classes B and F) because temperature variants would require different approaches for flow management. Classifications D and G can reflect hydrologic characteristics influenced by particular underlying geology –most notably the Carolina slate belt formation. However, these two classifications can also reflect hydrology affected by land use, impervious surfaces, numerous small impoundments and other alterations. These two classifications were subdivided with the latter case falling into the "accidental" category of the subdivision. 301/18/2011 SAB Presentation NC Stream Classes –Final 1.Class ACoastal Streams 2.Class B1 Small Stable Streams, Cool 3.Class B2 Small Stable Streams, Cold 4.Class CLarge Stable Streams 5.Class D1 Small Flashy Streams, Natural 6.Class D2 Small Flashy Streams, Accidental 7.Class ELarge Piedmont Rivers 8.Class F1 Medium Stable Streams, Warm 9.Class F2 Medium Stable Streams, Cool 10.Class G1 Small Seasonal Streams, Natural 11.Class G2 Small Seasonal Streams, Accidental 311/18/2011 SAB Presentation Google Earth Demonstration http://www.ncwater.org/Data_and_Modeling/eflows/kml/ Allows user to view currently classified streams (i.e., those with sufficient gage data) with other data layers. At this time geology is the only layer available. 321/18/2011 SAB Presentation