CLIMATE SMART FARMING

#2 Water: Some Lessons from the last 20 years in the Bega Valley

This Climate Smart Farming Topic is our first on water and will give a short summary. Later topics will cover water impacts and strategies in more detail.

Between 2000 and 2020 rainfall across south eastern Australia has been 15-20% below long-term average rainfall. These rainfall declines have been experienced across the Bega Valley. Reduced rainfall has also been accompanied by hotter temperatures, more extreme heatwaves and an increase in strong, hot winds.

These changing conditions are the expected outcomes of climate change in this region. What do these conditions mean for our farming and food production? What can we do to reduce their impact? These are some of the important questions behind SCPA's Climate Smart Farming project.

Agriculture is the sector which uses the largest volume of water, usually seventy percent or more in any large river basin or water catchment area. As farmers we have a major role and interest in adapting to changing rainfall conditions. We need to focus on using water as efficiently as we can, slowing water moving across the landscape, building and protecting our soils to better store water, reusing and recycling and increasing our water supplies with clever approaches to water infrastructure.

Water use efficiency

Water efficiency is the starting point. Analysis across the world and our experience and observation across the far south east shows that large gains can be made through using water as efficiently as possible. We can:

• monitor and fix any leaks in water delivery systems,
• adjust the timing of irrigation and watering to avoid evaporation,
• install more efficient irrigation, for example dripper systems under the surface or under mulch, so that more water reaches the roots of our crops, rather than evaporating,
• understand how moist our soil is by observing and testing it - we can use simple moisture sticks, dig pits and use our hands to feel the level of moisture, use simple in field testing kits, through to moisture probes and lab analysis of soil tests,
• know how much water our plants need and keeping our irrigation to what is needed (overwatering will waste water and will reduce fruit and vegetable quality and taste, and increase the risk fungal attacks),
• adapt our watering systems, plant selection and design and planting procedures to develop deeper stronger root systems and combinations of plant types to use water stored at different levels in the soil profile,
• select those crops and varieties that can withstand drier conditions better and use water more efficiently.

Keeping water in our landscapes

To reduce the water we loose from our landscapes we can slow the way it moves to reduce runoff and we can plan our landscapes and adjust our farming practices to reduce evaporation. Our cleared farm landscapes, often with soils compacted by decades of grazing by hard hooved animals have accelerated water runoff across our landscapes. Far less water is infiltrating into the soil and in dry times, far less is available to plants. This situation is worsened in the sloping lands of the Bega Valley. Several of the farms in the first stage of our Climate Smart Farming project were investigating ways to slow water movement down their farm slopes and gullies. Farmers can regenerate water depleted landscapes by ensuring their soil is not left bare, planting vegetation and building berms across the contour to slow water movement, and constructing contour swales to capture water and give it time to infiltrate into the soil.

Increasing the shade and reducing the wind shear across the landscape will reduce evaporation. Strategies include design of revegetation and crop plantings, use of structures as windbreaks and shade shelters and keeping the soil covered with plants and mulch.

Building the soil water reservoir

The soil is our most important water reservoir. With a porous soil, rich in organic matter which will bind with water and nutrients, we have much lower irrigation needs and can make much better use of that irrigation. Strategies to build the soil’s water holding capacity include increasing soil organic matter by adding composts and manures, no till practices to maintain soil structure and organic matter, keeping soil mulched and/or covered by plants, preventing compaction from concentration of hard hooved animals or machinery and vehicle pressure, and planting to encourage the development of a healthy root zone with pores of different sizes and reduce the risk of compacted subsurface layers.

Reuse and recycling

There are good opportunities for water reuse in rural as well as in urban and industrial systems. Reusing and recycling has benefits for both water security and for surrounding aquatic environments. There are important public health requirements in planning reuse and recycling, but there is technology now available in safe reuse and recycling at a range of scales from backyard greywater systems, to whole of city recycling. There are many opportunities across our households and farms. Examples can range from the low-cost level such as a bucket beneath a shower, to a septic recycling system delivering to trees, to major dairy recycling systems and city level wastewater reuse. As water is becoming scarcer and technology is increasing the opportunities to recycle at different scales, the cost benefit of implementing reuse and recycling is increasing.

Water infrastructure

Some farms pump water from rivers and streams. Some farms have bores to access groundwater and a few farms have access to town water supplies. Most farms will store rainwater in tanks, mostly for domestic use. There are large tanks now on the market which are being used as farm supplies. Covered tanks hold much less water than dams, but have the advantage of preventing losses to evaporation. Many farms in the Valley, however, rely heavily on farm dams for livestock, and to water crops and gardens. Most of the farms in the first stage of SCPA’s Climate Smart Farm project relied on farm dams.

Farm dams are often shallow, with little shade from surrounding vegetation and exposed to the strong winds. During droughts dam water evaporates rapidly and farmers can be forced to carry water to keep animals and plants alive. Strategies to save and increase available dam water can include:

• planning revegetation to increase shade and reduce wind shear across dams,
• covering dams with manufactured materials or with vegetation (including the use of floating islands on dams to produce food crops which, while they use water in the production of food, also reduce the evaporation from the dam),
• Increasing runoff into dams using contour swales and, in some cases, capturing the runoff from a road or track,
• Increasing dam capacity by digging the sediments out of the bottom or enlarging the dam.

It is important in adopting any strategy to recognize that building bigger dams or increasing the water pumped from rivers, streams and groundwater can make less water available to people downstream and to river and stream environments. Bigger dams and more dams will also increase evaporative losses across the region. Water use and water withdrawals must be consistent with water resource plans, water pumping rules and water licences.

Choosing and planning your farm

If you are new to farming and to the region, think carefully about what you want to do, and what you can do on your farm. Talk to others in your area with experience. Plan ahead for the long dry periods and realise that water you have this year may need to last for several years. Investigate and seek advice on what sort of crops you can grow with the water resources you have available and what are the water needs of any animals you have, including in hot, dry times. Observe the shade and wind effects across your farm and design your farm, including revegetation and planting areas, to save water and use it efficiently.