Conceptual Ecological Model of San Acacia Reach of Middle Rio Grande River – 2/13/07 1 st Draft Ibis Ecosystem Associates, Inc. Diversion & Regulation of Stream Water Structural Alteration & Development of Floodplain Discharge of Contaminants Into Stream System Degraded Water Quality Introduction and Spread of Non-native Vegetation River Channel Fragmentation Floodplain Loss & Fragmentation High Temperature, High pH, Low DO Barrier to Upstream Movement of Silvery Minnow Severe Flow Reductions Loss of Natural Variability In Annual & Seasonal Discharge Pattern & Hydrograph Hydrologic Degradation of River Channel Habitat: Reduced Magnitude & Duration of Spring Peak Flows Reduced Flowing Water With Low-Moderate Currents Narrowing of River Channel Reduced Over-bank Flooding in Spring Dewatering of River Channel & Formation of Isolated Pools Reduced Sand and Silt Substrates Reduced Eddies From Debris Piles, Pools, & Backwaters Saltcedar Proliferation Loss of Persistent Moisture Levels & Wetland Habitats In Riparian Areas Increased Fire Frequency & Intensity In Riparian Areas Loss of Dynamic Cycles Of Riparian Habitat Succession Loss of Connectivity Between Floodplain & Native Desert Habitat River Channel Habitat Quality: Perennially Flowing River With Peak Spring Flows and Over-bank Flooding Aggrading River With Shifting Sand Substrate Sinuous, Braided River That Freely Migrates Across Floodplain, Producing Eddies From Debris Piles, Pools, & Backwaters Floodplain Habitat Quality: Persistent Moisture Levels & Wetland Habitats in Riparian Areas Highly Variable Mosaic of Ephemeral Wetland Habitats, Supporting Willow & Cottonwood Stands Adjacent to Wetland Areas Unfragmented Landscape of Wide Lateral Extent, With Riparian Habitat Connected to Native Desert Habitat Rio Grande Silvery Minnow Southwestern Willow Flycatcher* Floodplain Lowered Water Table Drivers Stressors Effects Attributes * Impact of cowbird on flycatcher nesting to be covered in text.

Conceptual Ecological Model of San Acacia Reach of Middle Rio Grande River – 10/07 Draft Diversion & Regulation of Stream Water Structural Alteration & Development of Floodplain Introduction & Spread Non-Native Vegetation River Channel Fragmentation Floodplain Loss & Fragmentation Barrier to Upstream Movement of Silvery Minnow Severe Flow Reductions Loss of Natural Variability In Annual & Seasonal Discharge Pattern & Hydrograph Hydrologic Degradation of River Channel: Reduced Magnitude & Duration of Spring Peak Flows Reduced Channel Avulsion During Spring Peak Flows Reduced Over-bank Flooding During Spring Peak Flows Reduced Flowing Water With Low-Moderate Currents Narrowing of River Channel Dewatering of River Channel & Formation of Isolated Pools Reduced Sand and Silt Substrates Reduced Eddies From Debris Piles, Pools, & Backwaters Loss of Persistent Moisture Levels & Wetlands In Riparian Areas Increased Fire Frequency & Intensity In Riparian Areas Loss of Dynamic Cycles Of Riparian Plant Succession, Producing Dense Even-aged Stands, & Resulting In Loss Of Habitat Mosaic Loss of Connectivity Between Floodplain & Native Desert River Channel Quality: Natural Variability In River Flow Dynamics, With Peak Spring Flows, Avulsion, & Over-bank Flooding Aggrading River With Shifting Sand Substrate Sinuous, Braided River That Freely Migrates Across Floodplain, Producing Eddies From Debris Piles, Pools, & Backwaters Floodplain Quality: Persistent Moisture Levels in Wetlands & Riparian Areas Highly Variable Mosaic of Ephemeral Floodplain Communities, Supporting Willow & Cottonwood Stands Adjacent to Wetland Areas Non-fragmented Landscape of Wide Lateral Extent, With Floodplain Connected to Native Desert Rio Grande Silvery Minnow Southwestern Willow Flycatcher Floodplain Lowered Water Table Drivers Stressors Effects Attributes Altered Physical & Chemical Characteristics Of River Water: Reduced Sediment Load Reduced Temperature Increased Ammonia Aquatic Communities: Viable Populations of Key Indicator Groups of Aquatic Fauna Aquatic Fauna Community Diversity Marsh Communities: Creation of New Marshes Persistence of Established Marshes Cottonwood – Willow Communities: Seedling Recruitment Persistence of Established Communities

Conceptual Ecological Model of Working Hypotheses Aquatic Communities San Acacia Reach of Middle Rio Grande River 10/07 Draft Recruitment-Level Flow Events April-June 3,000 – 4,000 cfs 2-Week Duration 3-Year Frequency Hydrologic Connectivity River Channel to Floodplain Surface Water to Groundwater Episodic Flow Events Channel Avulsion & Scouring Backwater Nursery Habitat Viable Populations of Key Indicator Groups of Aquatic Fauna (Including Rio Grande Silvery Minnow) Aquatic Fauna Community Diversity Over-bank Flow River & Floodplain Management Hydrologic & Geomorphic Effects Performance Measures Aquatic Community Attributes Persistent Pools As Aquatic Refugia During Dry Periods Bank-full Flow & Dynamic In-Channel Morphology Recruitment To Adult Stage Survivorship By Age Class Population Geometric Growth Curves Diverse Sediment Size Distribution & Shifting Sand Substrate Prevention of Stranding With Water Level Recession Aquatic Habitat Heterogeneity: Multi-Threaded Channel Dynamic/Avulsive Channel Channel Width/Depth Ratio Backwaters Woody Debris

Conceptual Ecological Model of Working Hypotheses Marsh Communities San Acacia Reach of Middle Rio Grande River 10/07 Draft Maintenance-Level Flow Events 3-Year Frequency Hydrologic Connectivity River Channel to Floodplain Surface Water to Groundwater Episodic Flow Events 7,000 – 10,000 cfs 1-week Duration 10-Year Frequency Channel Avulsion & Scouring Bank-full Flow & Dynamic In-Channel Morphology Water Level Fluctuation Minimum 3-Foot Fluctuation < 3-Year Frequency Marsh Community Maintenance: Marshes Sustained by Surface Water & Groundwater Marshes Sustained Entirely By Groundwater Marsh Community Creation: Active Channel Marsh Communities Marshes Sustained by Surface Water & Groundwater Marshes Sustained Entirely By Groundwater Over-bank Flow River & Floodplain Management Hydrologic & Geomorphic Effects Performance Measures Marsh Community Attributes Site Preparation & Management Removal of Non-Native Vegetation Fire Management Other Groundwater Level Longevity and Succession Of Established Marshes Marsh Community Maintenance: Active Channel Marshes Frequency, Location, & Spatial Coverage of Newly Created Marshes Spatial Coverage of Each Marsh Community Type

Conceptual Ecological Model of Working Hypotheses Cottonwood - Willow Communities San Acacia Reach of Middle Rio Grande River 10/07 Draft Recruitment-Level Flow Events < 5-Year Frequency Hydrologic Connectivity River Channel to Floodplain Surface Water to Groundwater Episodic Flow Events Channel Avulsion & Scouring Water Level Fluctuation Soil Wetting May-June Maximum Groundwater Recession Rate of 2 – 4 cm/day Persistence of Established Cottonwood & Willow Communities Successful Recruitment Of Cottonwood & Willow Seedlings Over-bank Flow River & Floodplain Management Hydrologic & Geomorphic Effects Performance Measures Cottonwood/Willow Community Attributes Site Preparation & Management Removal of Non-Native Vegetation Fire Management Other Groundwater Level: Depth To Groundwater Of 3 – 6 Feet Frequency, Location, & Spatial Coverage Of Seedling Recruitment Of Cottonwood and Willow Location, Spatial Coverage, & Longevity Of Established Cottonwood & Willow Communities Creation of Scoured Habitat For Seedling Recruitment, Formation of Bars and Islands For Willow Establishment