water cycles

subject:	water cycles govern all things in life.
problem:	we are severely disrupting the planetary water systems; if we are not to run out of usable water, we must understand more clearly these cycles and our inextricable relationship with them.

We seldom experience water in any profound or meaningful way, so our relationship with it is limited. We need to understand the way water moves within the world, to better appreciate how we should deal with it, what we should and should not do, as individuals, but also as a global society.

problem:

The world is running out of usable water; not just in third-world countries, but in many of the developed nations also, where per capita water demand is far higher. Coupled with exponential population growth and global warming, this means we are in trouble. It is true that water can never be removed from the planet - on a global scale, it is a closed loop system; but we can and are putting it rapidly beyond easy reach for our own use, and so, also beyond the reach of many natural ecosystems and micro-ecologies. Much of our current agricultural output depends on irrigation pumped from rivers and underground fossil aquifers that are rapidly being pumped dry. How long does a drink last if you suck out the contents with a straw? Not long for sure, and the same is true of our water supplies.

solution:

By understanding our interaction and effects on the hydrological cycles, and especially the small hydrological cycle, we can act to prevent the loss of water from where we need it most: in the soil, in biomass, in the watertable and in the atmosphere. These cycles are literally the Gaian life-blood of the planet, and no living organism can survive without good circulation; we must harmonise our activities with these cycles, so that we naturally enhance them, rather than deplete them.

What is important here is to understand that the small water cycle - water that evapourates from land, forms clouds and falls again as rain within the same region - is profoundly important to the well-being of that land and what we do affects it fundamentally, for good or ill. In this respect, modern agricultural methods - in fact, agriculture in all its forms, has a significant impact.

Vascular plants act as the skin of the Earth; they are the vessils which regulate hydrological water flow through transpiration, absorbing and allowing percolation of water into the soil (witness the soil erosion when trees are removed) and re-emitting moisture to the atmosphere, 40,000 litres per hectre per day (T. Schwenk 1962). Trees only retain about 1% of the water they absorb, in the process of photosythesis. Thus trees act as conductors of water, they hold and allow water to infiltrate the soil, they draw moisture from deep levels and return it to the atmosphere. Remove the trees and the circulatory system becomes broken; local air moisture content diminishes and rainfall becomes eroding torrents, washing away topsoil and by not percolating into the ground, causing water table levels to drop. The volume of rain that falls will also diminish as the effects of deforestation continue.

Combined with abstraction for irrigating crops and the relatively low Leaf Area Index (LAI) of crops compaired to forest and you have a situation where the land will dry out over time. Furthermore, irrigation causes a build up of salinity within the upper soil levels (mineral salts which trees hold at deeper strata), ultimately rendering the land unusable.

The answer to this is actually very simple - plant and nourish trees, give cover to the soil, increase biomass, and the soil will rehydrate, returning the land to health and bringing the rain. The difficult thing is finding the political will to make this happen. Fortunately, there are many, many good reasons for doing this, especially when combined with the philosphy of forest gardening and rain gardens. Fortunately, we don't have to wait for government to do something about this, it's easy to do within your own patch of land, and within your neighbourhood. Community action and lobbying can shift mountains.