Hydraulic Connectivity. Jim Rogala, USGS September 28, 2016

Transcription

1 Hydraulic Connectivity Jim Rogala, USGS September 28, 2016

2 Connectivity why do we care? Example: Centrarchid fish in winter I can t breath!!! I m too cold!!! Just-right connectivity Low connectivity High connectivity

3 Connectivity From Lubinski et.al.: Lateral connectivity Habitat connectivity Flood pulse connectivity Lateral non flood connectivity Main stem/tributary connectivity Sub surface connectivity Longitudinal connectivity

4 Isolated backwater lakes Backwater connectivity types Water exchange a function of: Connectivity is primarily a function of frequency of connection (binary) Ground water Inundation exchange important tool developed in some by cases Tim Fox HREPs could alter with levee building or breaching Unlikely HREPs could alter but consider when evaluating projects There s been few HREPs that have altered connectivity of isolated backwaters. Potential for more of these, especially in the lower river. RECONNECTION

5 Backwater connectivity types Contiguous backwater lakes Two ways to consider connection: Connection at low to moderate discharge (non flood) Connection when natural levees over topped (flood pulse) Note: water exchange can vary within lakes.

6 Backwater connectivity types Single connection backwater lakes Water exchange a function of: Water level fluctuation Size of connection Location of connection Bathymetry Temperature Dissolved Oxygen Dam 8 Elevation Single connection Channel HREPs Island building Surface Bottom Multiple connections Direction of channel flow Connectivity Low Month/Day Channel Location Presence Size Volume of of connection depression High

7 Backwater connectivity types Single connection backwater lakes Water exchange a function of: Water level fluctuation Size of connection Location of connection Bathymetry Ground water exchange Spillway HREPs have altered connectivity of single connection backwaters through dredging (bathymetry) and island building. Open water in winter indicating ground water inputs Could alter to change to multiple connection backwater. Opportunity for water level fluctuation control?

8 Backwater connectivity types Multiple connection backwater lakes Water exchange a function of: Connectivity planform surrogate metrics Low HREP dredge/fill High Size of inlets/outlets Number of inlets/outlets Arrangement of inlets/outlets Total size Shoreline complexity

9 Backwater connectivity types Multiple connection backwater lakes Water exchange a function of: Connectivity bathymetric surrogate metrics Low HREP dredge/fill High Volume Presence of depression Connection cross-section

10 Backwater connectivity Water exchange predicted by surrogates: Low High Percent of perimeter that is channel Winter habitat suitability for centrarchic fishes Number of connections to channels

11 Backwater connectivity HNA II HREPs selected to address existing and future needs derived from HNA II HNA II will include enhanced aquatic area classes that include connectivity metrics derived from planform metrics

12 Backwater connectivity Water exchange measured as velocity (modeled): HREP island construction results in areas of reduced connectivity 2 D hydraulic models are often part of project planning and evaluation

13 Backwater connectivity Water exchange directly measured as velocity: Trends in velocity using SRS data Mean water speed decreased over the study period However, after adjusting for discharge, no detectable trend.

14 Backwater connectivity associations Nutrient associations with connectivity Nitrogen associated with connectivity DIN (mg L -1 ) Beiers Lake Lawrence Lake Markle Lake French Lake Target Lake Round Lake Broken Arrow Swift Creek Shady Maple Horseshoe Low Connectivity High

15 Backwater connectivity associations Biological associations with connectivity Metapyhton associated with connectivity

16 Backwater connectivity within lake considerations Low High Some variability can be captured at the lake scale. Connectivity metrics based on proportion of some condition. Metrics as minimum amount of some condition

17 Backwater connectivity within lake considerations Trends in velocity using SRS data Slight positive trend found for within lake variation. The occurrence of BDL values (< 2 cm/sec ) was found to be increasing. These changes might be best explained by recent increases in vegetation. within among

18 Backwater connectivity within lake considerations Overlay of 2008 SAV sampling and 2008 modeled probability of SAV SAV in deeper locations. No SAV in somewhat shallow locations. Modeled probability HREP driven science Rake grabs with SAV *

19 Backwater connectivity within lake considerations A simple sediment transport model Estimating water exchange using cost*distance SAV in deeper locations. No SAV in somewhat shallow locations. Modeled connectivity (cost*distance) Low High

20 Connectivity how do we use it to manage? Example: Centrarchid fish in winter I can t breath! I m too cold! Low connectivity High connectivity Add connection to deliver more channel water Build islands to shelter an area from flow Much better!!! Thanks!!!