What keeps the awa (river) flowing when we have a month with virtually no rain? By the end of January, Whanganui's official rain gauge had recorded a paltry 0.2 mm. Upriver the areas without trees were a parched, dead-looking colour that some folks euphemistically call "golden". The deforested areas didn't look like the source of the relatively low but clear and steady flows in the awa, and steep slopes covered in dead grass have always been at risk of slipping in the next deluge.
What did keep the river running were nature's sponges that soak up during plentiful rain then generously do a slow release of filtered water during the dry periods. Much of this goes on underground, and is why aquifers - the underground reserves moving through sand and shell rock layers - are real treasures. Sadly, ancient aquifers worldwide are collapsing from over-extraction. There is no room for a "she'll be right" attitude when the Three Waters review goes forward. We need to work smarter as demand grows.
The other sponges of life-giving water can be seen at ground level. They are the healthy soils and wetlands that have survived changes in the mosaic of land use in our region. Healthy soils, especially those under forest, have an intricate structure. It can be half living material as well as minerals. Networks of plant roots interact with even greater networks of fungi and bacteria that maintain life by running nutrient cycles. Respect is the word that comes to my mind when I think of the wisdom accumulated in the DNA of all this life.
Healthy soils absorb and hold water the way a sponge does. They soften the peak flows going into rivers and so they are our first line of defence against flooding. When the dry comes, there is still some percolating water trickling into the small creeks that join together to make the awa flow. It is great to see the farmers who are planting trees to stabilise their steeper slopes and conserve the soils that are left.
Swamps and wetlands are the prizewinners for life-sustaining water management. In them the onslaught of heavy rainfalls is given a break on its downhill run, and that naturally gives us a break from the worst of flood peak flows. Even city engineers have started to understand this and are rebuilding wetlands into their stormwater management and public amenity planning. Such a turnaround from the contempt with which some previous generations regarded wetlands as they raced to fill them in or dig drains around them to hasten the water "away".
