Small Dams: Planning, Construction and Maintenance has been written to provide a practical approach and guide to determining catchment yield and the amount of water required in a dam, advising on selecting and working with engineers and contractors, as well as outlining the cause of dam failures and how to remedy problems quickly. It also covers relevant legislation, environmental and ecological issues.
Employing the principles in this book, in conjunction with heeding the advice of suitably experienced and qualifi ed engineers and contractors, will reduce the risk of failure and help to ensure the long term success of any small dam in question. Small Dams will be an invaluable resource for anyone who owns a dam, and a useful reference for agencies, contractors and engineers.
The author, Barry Lewis, has over forty years of experience as an engineer and has written extensively on farm dams, soil conservation, catchment management and the environmental impact of dams both on and off streams. He was also directly involved in the licensing and regulating of small dams in Australia.
Section 1 Planning
1.1 Assessing water needs
1.1.1 Planning water supplies
1.1.2 Water quality
1.2 Assessment of catchment yield
1.2.1 Factors controlling catchment yield
1.2.2 Methods of estimating catchment yield
1.2.3 How trees affect yield
1.2.4 Artificial catchments
1.3 Dam site selection
1.3.1 Choosing a dam site
1.4 Types of farm storages
1.4.1 Gully dams
1.4.2 Hillside dams
1.4.3 Ring tanks
1.4.4 Turkey’s nest tanks
1.4.5 Excavated tanks
1.4.6 Weirs
1.4.7 Off-waterway storages
1.5 Dam storage size
1.5.1 Evaporation losses
1.5.2 Ways of controlling evaporation
1.5.3 Seepage losses
1.5.4 Average water consumption
1.6 Using a dam in drought
1.7 Fire fighting
1.8 Small dams and trees
1.9 Dam cost justification
Section 2 Investigation
2.1 Soil testing
2.1.1 Foundation
2.1.2 Borrow pit for embankment material
2.1.3 Spillway site
2.2 Site selection criteria
2.2.1 Seepage losses
2.2.2 Stability of dam sides
2.2.3 Sedimentation in dams
2.3 Foundation materials
2.4 Embankment materials
2.5 Site investigation of materials
2.5.1 Soil texture tests
2.5.2 Unified soil classification
2.6 Analysis of soil
2.6.1 Core trench
2.6.2 Embankment soil
2.7 Location of soil
2.8 Unsuitable material
Section 3 Design
3.1 Items that need to be considered
3.1.1 Embankment types
3.1.2 Core trench
3.1.3 Embankment batter slope
3.1.4 Crest width
3.1.5 Freeboard
3.1.6 Alternative ways of batter protection
3.1.7 Topsoil cover
3.1.8 Fencing
3.2 Flood flow estimation
3.2.1 Peak flow estimation
3.3 Outlet structures
3.3.1 Earth spillways
3.3.2 Design spillway capacity
3.3.3 Selecting spillway dimensions
3.3.4 Chute spillways
3.4 Pipelines through embankments
3.4.1 Trickle pipes
3.4.2 Drop inlet structures
3.4.3 Cut-off collars
3.5 Earth and water computations
3.5.1 Embankment material
3.5.2 Floor slope
3.5.3 Area beneath embankment
3.5.4 Excavated tanks
3.5.5 Water storage capacity computations
3.5.6 Storage excavation ratio
3.6 Estimate of costs
3.6.1 Economics
3.6.2 Dam quality pays over time
Section 4 Documentation
4.1 Collation of plans and specification
4.2 Collecting basic design data
4.2.1 Catchment map
4.2.2 Location (topographical) map
4.2.3 Profiles and cross-sections
4.2.4 Soils
4.3 Assembly of data
4.3.1 Analysis of data
4.3.2 Design
4.4 Construction documents and drawings
4.4.1 Specifications
4.4.2 Checklist
4.5 Final review and approval
4.5.1 Records
Section 5 Construction
5.1 Approval for dam building
5.1.1 Details that may need to be submitted
5.1.2 Referral dams
5.2 Selecting your dam builders
5.2.1 Selecting an engineer
5.2.2 Details that an engineer can provide
5.3 How to build a dam
5.4 Steps in constructing a dam
5.4.1 Setting out
5.4.2 Diversion of water
5.4.3 Clearing and grubbing
5.4.4 Stripping topsoil
5.4.5 Core trench
5.4.6 Borrow pit material
5.4.7 Selection and placing of material
5.4.8 Spillway and outlet structures
5.4.9 Batters and topsoil
5.5 Compaction
5.5.1 Compaction when constructing a dam
5.5.2 Recommendations for compaction
5.6 Soil moisture
5.6.1 Adjusting soil moisture
5.7 Allowance for settlement
5.8 Equipment
5.8.1 Rollers
5.8.2 Features of roller compaction
5.8.3 Other machinery
5.9 Installation of outlet pipe
5.9.1 Testing of the pipe
5.9.2 Foundations on rock
5.10 Checking for compliance with standards
5.10.1 Checking the contractor’s work
5.10.2 Inspection during construction
5.10.3 Good work takes time
5.10.4 Extra ‘bonuses’
5.10.5 Changing your mind
5.10.6 Progress payments
5.11 Final inspection and measurements
Section 6 Maintenance
6.1 Safety surveillance
6.1.1 Equipment for inspection
6.1.2 Observations to be recorded
6.2 Inspection procedures
6.2.1 General techniques
6.2.2 Specific techniques
6.2.3 Evaluation of observations
6.2.4 Frequency of inspection
6.3 Causes of dam failures
6.3.1 Dispersive clays
6.3.2 Seepage and leakage
6.3.3 Cracking and movement cracks
6.3.4 Erosion
6.3.5 Deformation and movement
6.3.6 Defects in associated structures
6.3.7 Vegetation
6.3.8 Total catchment protection
6.3.9 Weed control
6.4 Dam leakage
6.4.1 Rebuilding
6.4.2 Use of soil additives
6.4.3 Artificial liners
6.4.4 Using a clay liner
Section 7 Water
7.1 Quantity
7.2 Water quality
7.2.1 Domestic use
7.2.2 Stock water
7.2.3 Irrigation water
7.3 Water treatment for human consumption
7.4 Algae in farm water supplies
7.4.1 Problems
7.4.2 Identification
7.5 Salt in dam water
7.5.1 Minimising salinity in dams
7.5.2 Interception of sub-surface saline water
7.5.3 Maintenance
7.5.4 Downstream effects
7.5.5 Minimising the effects of evaporation
7.5.6 Stock and salty water
Section 8 Ecology
8.1 Wildlife and plants in dams
8.1.1 Water regime
8.1.2 Basic topography
8.1.3 Vegetation
8.1.4 Grazing by stock
8.1.5 Waterways and swamps
8.1.6 The role of hunting
8.1.7 Waterfowl management
8.2 Water plants in dams
8.2.1 Aquatic plants
8.3 Using herbicides near water
8.3.1 Hazards
8.4 Vegetation on and around dams
8.5 Yabbies
8.5.1 Physical removal
8.5.2 Biological removal
8.5.3 Chemical control
Section 9 Commercial
9.1 Fish farming
9.1.1 Established freshwater species
9.1.2 Dam conditions that control productivity
9.1.3 Feeding
9.1.4 Aquatic vegetation
9.1.5 Fish loss by escaping
9.1.6 Muddy water
9.1.7 Algae
9.1.8 Other species
9.2 Yabby farming
9.2.1 Types of dams for yabby production
9.2.2 Water properties
9.2.3 Stocking and feeding
9.2.4 Harvesting
9.3 Native fauna and total ecosystem management
9.3.1 Native fauna
9.3.2 Managing predation by native fauna
9.4 Licensing process
9.4.1 Licences required
9.4.2 Other steps that may need to be taken
Section 10 Legal
10.1 Legal and policy aspects in Australia
10.2 Liability
10.3 Responsibility of dam owners
10.3.1 Liabilities of dam owners
10.3.2 Permission to build a dam
10.4 Dam failure
10.4.1 Potential hazard and risk of small dams
10.4.2 Minimising the risk of dam failure
10.4.3 In case of dam failure
10.4.4 Abandonment of small dams
10.5 Designer and earthmoving contractor(s)
10.6 Property insurance
References and suggested further reading
Appendix 1 Glossary of terminology
Appendix 2 Engineering specification for an earth-fill farm dam
Appendix 3 Metric and imperial conversion tables
Biography
Barry Lewis has over thirty years of experience as an engineer and has written extensively on farm dams, soil conservation, catchment management and the environmental impact of farm dams both on- and off-stream. He is directly involved in the licensing and regulation of farm dams in Victoria, Australia.
