WATER
Water earthworks
Water is a rare mineral, in the form of potable water, water that is safe to drink and found naturally. It is the world most critical resource. Fresh water is only 3% of all water on Earth the rest is salt water in the oceans.
Of the fresh water:
75% – Ice sheets and glaciers
# 11% – Available ground water, less than 800m
14% – Deep groundwater and aquifers 800 to 4000m
100%+ or – the remainder is so small it is nearly insignificant.
# 0.3% – Lakes and ponds at the surface
# 0.06% – Soil moisture and forests
0.03% – Rivers
0.035% – Atmosphere
# These are the storages we can influence locally.
The duties of water:
1. To procreate life in growing systems.
2. To develop productive aquaculture systems.
3. To develop hydraulic uses for energy production, pumping water, generating electricity and mechanical take-off.
The idea is to use water as many times as possible before it
passes through the system. Increasing life in a system increases potential yield.
In particular we can:
• Increase surface storage
• Reduce runoff
• Decrease evaporation
The essential techniques are:
• Increase soil storage by rehabilitation of compressed and sealed soils, using Keyline methods, including chisel plowing for increase aeration.
• Increase the soakage to high groundwater by excavating swales. A water harvesting channel on contour with a soft mound on the lower side made from the excavated material from the channel. Water is held momentarily from running away rapidly downhill and soaks in, trees planted either side will thrive. Water eventually slowly recharges ground water. Swales can vary in size up to 6m across the channel, depending on the size of the size and type of catchment.
• Reduce evaporation by mulching, which is an imitation of the forest floor leaf litter, preventing erosion and building up soils. This is easy to achieve in a small area, but over a large area mulch trees and shrubs need to be grown to produce surplus harvestable mulch.
• Increase small surface storages in the form of dams, ponds, small ponds in gardens, and tanks at houses for freshwater supplies.
Dams:
Types of dams need to be well understood;
Saddle dams position on a ridge between high points with 2 dam walls and fed by diversion drains and or swales. Very high positions possible as gravity irrigation dam.
Ridge dam positioned on a flatter spot on a ridge and fed by diversion drains and or swales. Usually a rounded crescent shape wrapped around the ridge, and curved dam wall, and high positions possible as a gravity irrigation dam.
Key point dam, the highest possible valley dam in any one valley, can be fed by diversion drains, often connects to other key point dams at the same corresponding contour with swales. Connections to ridge point dams are possible. A key point dam is usually a high gravity irrigation dam.
Valley dams are the usual dams in the landscape with the dam wall crossing a valley. They are the hardest to build and take the most maintenance. The further down a valley they are situated the bigger they usually get, the spillway always gets larger the further down the valley they are positioned because the total catchments area has increased. These dams make good life dams and edge feature dams, and can be used for flood irrigation.
Contour dams positioned on shallow slopes fed by swales at the back with swale integrated spillways. These can be good aquaculture dams as they are easily shaped and can be set up to be easily drained.
An ideal landscape would have 15%+ covered with dams and cater for this water with swales and ripped conditioned topsoil, then planted along swales. We should try to hold water as high as possible.
A strategy of water use in landscape is the longest path over the most time with the most passive friction is the most fertile.
Evaporation strategy:
Instead of one big dam, construct 3 smaller dams, one above the other. Use the top dam first till half empty, then use the second dam until half empty and then fill the second dam from the top dam, then use the second dam until half empty and the do the same with the third. This cuts the evaporation rate.
Large completely enclosed in ground roofed tanks can be used to collect water efficiently in deserts.
Most runoff occurs from sealed surfaces like roofs and roads.
Irrigation systems:
• Drip or trickle, especially in dry land situations.
• Flood irrigation.
• Under canopy.
• Sprinklers are not efficient and build up salt in the soil in dry land situations.
Components of irrigation system:
• Water source, bores, springs, soaks, runoff, swales, pipelines, creeks, tanks and lakes.
• Energy source, water at head pressure, pressure pumps electric, fuel, wind, hand or animal.
• Distribution network, net and pan, pipes, channels and buckets.
• Emitters, dripline, sprinkler and buckets.
Irrigation rules for arid regions:
• Irrigation under mulch to reduce salt problems and increase evaporation efficiency.
• Irrigate at dusk or at night if possible.
• Give long watering every 3 to 5 days, takes water down the trees roots are bigger in the cool of the soil and reduces leaching.
• Allow for leaching.