Here are some notes on the presentation held recently.
Summary from presentation by Craig Turton DPI, Tallangatta Valley Hall, Tuesday 14 October [Please note these notes are intended for general interest only]
Climate change or climate variability forecasts are suggesting there will be a reduction in average rainfall. A small reduction in rainfall results in a significantly greater reduction in runoff ie in general a 10% reduction in rainfall will result in a 40% reduction in runoff. This has significant implications for farm water supply, ie dams that were usually reliable will now become unreliable.
A farm water plan involves undertaking a Total Farm Water Balance, which means calculating how much water is required and how much water is available. The next step is to plan how to store and distribute this water efficiently.
The rule of thumb once was – for wetter areas, store enough water for 1 1/2 years, whilst dryer areas require storage periods of up to three years.
Water use includes that for garden, lawn, vegetables, orchard, trees, fire fighting, stock, cleaning and environmental benefits.
Roofed areas provide a great collection area and all large areas should have tanks on them
Need to increase smartness in how we use water.
Sources of water include springs (need to be confident of reliability) catchment dams (there was much discussion on the difficulty of putting in new ones!!), bores (putting them in hit and miss, $10-20,000 to put in, generally deeper as go down a catchment, may be the most reliable, pumping can be an issue) and rainwater
Soil type and topography limits dam placement
Types of storages include:- gully dam, hillside dam, ring tanks, turkey next dams, excavated tanks, weirs
A dry cow requires around 16,000litres a year and a milking cow 25,000litres, but intake will vary seasonally with weather conditions
Providing stock water in troughs allows stock to be grazed for increased pasture production through management choices.
Evaporation is usually 2m a year (rule of thumb), so the top 2m of a dam will evaporate, dams less than 1 meter will not be reliable. Dams need to be 4-6m deep to be reliable. All dams leak with seepage
Ideally springs should be fenced off to stop animals pugging them. Do not place dams on springs as the disturbance and weight of the water may harm or reduce the supply. Rather build the dam below the spring and put in an extraction system, subject to all regulations.
Most springs originate locally, a few result from large fissure fractures
Water reticulation should fit with farm plan, reticulation should be strategically located, accessible to stock, not lead to erosion or pollution and adequate for proposed usage.
Compared to a one inch pipe a two inch pipe conducts four times as much water.
Pressure delivers water through a pipe, some pressure is used to overcome friction loss.
1m water = 10 kPa = 1.4 PSI
1 litre of water into a pipe = 1 litre of water out of a pipe
Water is not compressible
Doubling the flow rate means that the velocity must be doubled too. For increased output of a pipe, the water will have to flow faster.
Pumps push water, they do not suck it
Pipes:- classes and pressures vary eg Rural B or imperial class, PN 10 safe working pressure, PN 2.5 safe working pressure
Ideally farm reticulation systems should be designed so that four days of water supply is stored in the tank. All troughs should be on the feed out line.
Craig is available to undertake farm planning and farm water planning on a request basis.
See the Landcare Website http://northeast.landcarevic.net.au/tallangatta-valley to read summaries of our visits to Simon & Phillipa Nobel’s and Rod Manning’s. The rest Rod Manning’s summary is on the website. See the great photo of Les C. Esquire long time happy resident of Tallangatta Valley!!.