United States Department of Drinking Water from Forests Agriculture Forest Service and Grasslands A Synthesis of the Scientific Literature Southern Research Station George E. Dissmeyer, Editor General Technical Report SRS-39 The Editor: George E. Dissmeyer, Water Quality Management— Nonpoint Source Consultant, 145 Lake Forest Drive, NE, Eatonton, GA 31024. Cover photo: Hendersonville Reservoir Dam, Pisgah National Forest, North Carolina. Photo by Bill Lea. _____________________________________________________________________________________________ The use of trade or firm names in this publication is for reader information and does not imply endorsement of any product or service by the U.S. Department of Agriculture or other organizations represented here. _____________________________________________________________________________________________ This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife—if they are not handled or applied properly. Use all herbicides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and their containers. September 2000 USDA Forest Service Southern Research Station Asheville, North Carolina Drinking Water from Forests and Grasslands A Synthesis of the Scientific Literature George E. Dissmeyer, Editor “after refreshing ourselves we proceeded on to the top of the dividing ridge from which I discovered immence ranges of high mountains still to the West of us with their tops partially covered with snow. I now decended the mountain about 3/4 of a mile which I found much steeper than on the opposite side, to a handsome bold runing Creek of cold Clear water. here I first tasted the water of the great Columbia river.” —from Meriwether Lewis’ journal, August 12, 1805 i Table of Contents Page Executive Summary ......................................................................................................................................... ix Part I: Introduction Chapter 1: Goals of this Report ...................................................................................................................... 3 Douglas F. Ryan and Stephen Glasser The Importance of Safe Public Drinking Water ................................................................................................. 3 Drinking Water from Forests and Grasslands..................................................................................................... 3 The Purpose and Scope of this Document .......................................................................................................... 4 How to Use this Document ................................................................................................................................ 4 Acknowledgments .............................................................................................................................................. 6 Literature Cited ................................................................................................................................................... 6 Chapter 2: Drinking Water Quality ................................................................................................................ 7 F.N. Scatena Introduction ........................................................................................................................................................ 7 Chemical Properties ........................................................................................................................................... 7 Physical Properties ............................................................................................................................................. 20 Biological Properties .......................................................................................................................................... 22 Literature Cited ................................................................................................................................................... 25 Chapter 3: Watershed Processes—Fluxes of Water, Dissolved Constituents, and Sediment .................... 26 F.J. Swanson, F.N. Scatena, G.E. Dissmeyer, M.E. Fenn, E.S. Verry, and J.A. Lynch Introduction ........................................................................................................................................................ 26 The Integrated Hydrologic System ..................................................................................................................... 26 Effects of Nitrogen Deposition on Stream and Ground Water Quality .............................................................. 32 Sediment Production and Transport ................................................................................................................... 34 North Santiam River Case Study ........................................................................................................................ 35 Natural Disturbance Processes ........................................................................................................................... 36 Cumulative Watershed Effects ........................................................................................................................... 37 Management and Policy Considerations ............................................................................................................ 37 Research Needs .................................................................................................................................................. 38 Key Points .......................................................................................................................................................... 39 Literature Cited ................................................................................................................................................... 39 Chapter 4: Economic Issues for Watersheds Supplying Drinking Water ................................................... 42 Thomas C. Brown Introduction ........................................................................................................................................................ 42 Cost Minimization .............................................................................................................................................. 43 Opportunities for Cost Savings .......................................................................................................................... 45 Complexity ......................................................................................................................................................... 47 Cost Savings from Targeting Upstream Control Efforts .................................................................................... 48 Bringing About an Efficient Cost Allocation ..................................................................................................... 48 Conclusion .......................................................................................................................................................... 50 Literature Cited ................................................................................................................................................... 50 iii Part II: Effects of Recreation and the Built Environment on Water Quality Page Chapter 5: Hydromodifications—Dams, Diversions, Return Flows, and Other Alterations of Natural Water Flows .................................................................................................................................... 55 Stephen P. Glasser Introduction ........................................................................................................................................................ 55 Effects of Dams and Impoundments on Water Quality ...................................................................................... 56 Water Diversion Structures and Water Import/Export Between Watersheds ..................................................... 57 Water Well Effects on Drinking Water Quality .................................................................................................. 58 Sewage Effluent and Sludge/Biosolids Applications to Forest and Rangeland ................................................. 58 Wetland Drainage ............................................................................................................................................... 59 Reclaimed Water and Return Flows ................................................................................................................... 59 Reliability and Limitations of Findings .............................................................................................................. 59 Research Needs .................................................................................................................................................. 60 Key Points .........................................................................................................................................................