Kauai Water Security

SUBHEAD: We must change the infrastructure now to address future water security on Kauai.

By David Ward on 10 October 2009 for Island Breath - 
(http://islandbreath.blogspot.com/2009/10/kauai-water-security.html)


Image above: The Puu Lua Reservoir in Kokee in the Kaulaula Ahupuaha of Kauai. From http://www.dailyventure.com/photo.php?name=kauai_helicopter_reservoir
 
The Garden Island, known for it's ample rainfall and verdant tropical landscape, is home to one of the wettest spots on earth. Why then, would we possibly ask our community to focus on our water supply when there are so many other critical energy issues to be addressed?

Volatile electricity costs, a crippled economy, food security, the list goes on. Simply put; in most Island homes, our water supply is completely oil dependent. Without petroleum to generate electricity, we simply cannot deliver water to a majority of Island residents on Kauai. And although some of our State and County leaders have recognized and begun acting on the real potential for oil supply disruptions and continued price volatility, as well as the general economic liability of severe dependence on tourism, few have asked; What about our water?

Kauai relies almost exclusively on pumped groundwater for its residents. Because of its purity groundwater has been preferred for municipal use. Pumping groundwater is one of the most expensive and energy-intensive ways of delivering water to consumers. This energetic dynamic needs reevaluation. The Department of Water (DOW) must now start to make our water system as resilient as possible and maximize energy efficiency and minimize our carbon foot print.

The existing thirteen (13) unconnected systems pump water from 48 underground wells, uphill to 43 tanks. The pipes leak so much that 25% of the water and energy are lost and un-metered (www.kauaiwater.org). This system evolved during a time when there was abundant water and before the current concern about the future of fossil fuels and global climate change.

Kauai depends almost entirely on foreign sources of fuel for its energy needs. High global demand for oil is linked with Kauai's electricity pricing, which is more that three time the national average. The island is vulnerable to fluctuations in the world oil market and sends millions of dollar each year out of the local economy. Every barrel of fossil fuel we use now is subtracted from the total available to our descendants; no other resource can provide anything approaching the glut of cheap abundant energy on which our lifestyles of relative privilege depend.

Energy transitions happen and we are in one now and we need to aggressively look to the future. What is going to happen after petroleum. Modest as the energy outputs from alternative sources are, they are all we well have to work with when the fossil fuel is gone. Oil production will likely drop a lot faster than our co-op, KIUC ability to invest in and bring on alternatives. It is an unprecedented discontinuity of historic proportions, as never before has a resources as critical as oil become scarce without sight of a better substitute. To replace the oil we are losing by depletion, investment in renewables would have to be an order of magnitude higher than current spending.

On average throughout the islands, one-third of rainfall runs into streams, one-third evaporates and transpire (after being taken up by plants), and one-third recharges the underground water.

Because of kauai's comparatively advanced age its original form has been greatly modified by erosion and the island has evolved a more complex geologic structure and stratigraphy than any of the other Hawaiian islands.

The Hawaiian Islands are formed by shield volcanoes, so called because of a resemblance in profile to round shields of early warriors. Their eruptions were relatively gentle, spreading thousands of thin layers of lava as the land was built up. Each flow averages 12 to 15 feet in thickness and are highly permeable.

As the shields of lava poured out and cooled, cracks would form in the shields. Subsequient flows would sometimes erupt below the shields and these subterranean flows would extrude their way upward through the cracks. Because these later flows were under pressure from the weight of the old lava beds above, they are dense and impervious to water. The result is an intermingling of large deposits of porous basalt, saturated with percolating rainwater, restricted in there lateral flows by hundreds of dikes.

Groundwater can occur at high elevations because of the presence of these dikes. The vertically confined water rises until it leaks through the dikes and reach equilibrium with the rate of recharge from the rain above. These dike-impounded, high elevation ground waters can result in columns of water hundreds feet high on the windward side of the island, where the moisture-laden trade winds bump up against cliffs several thousand feet high and disgorge their moisture as rain.


Cap rock consisting of a bed of dense lava, volcanic ash, or alluvium can and does occur at high elevations on Kauai. Where the dense layers of packed sediment cover the freshwater-saturated basalt, rainwater collects over this cap rock, forming reservoirs of water, or perched groundwater.

Freshwater springs flow through breaks in the impervious rock. Similar breaks connect the aquifers, sometimes so much that withdrawals from one also significantly drains the other. In these cases, although different aquifers are involved, they act as one "hydrologic unit". I think David Craddick, manager and chief engineer of the Department of Water, is right, it is all the same
water
only the location of the tap is changed.

Down near sea level, highly permeable basalt is a repository for reservoirs of fresh water. Because of this permeability sea water moves laterally through the rock. Fresh water is lighter than saltwater and floats on the saltwater. The fresh water that sits on the saltwater is known as basal groundwater.This freshwater takes the shape of a biconvex lens, with both the top and bottom bulging outward.

Saltwater encroaches on the fresh water aquifer at or near the seashore, and springs of fresh water may discharge at or near the seashore or even offshore.

Where the water table intersects the ground surface, ground water may discharge at springs and along streambeds. This discharge maintains a base flow in the streams even when there is no direct runoff from rain.

If withdrawal from wells is excessive, saltwater may rise and intrude the wells. Saltwater intrusion is a major limitation to well yields in oceanic island aquifers. Well withdrawal has the eventual effect of lowering the water table and reducing stream flow and ocean discharge.

The ahupua'a system of traditional Hawaiian communities (running from the mountain to the sea) contained all the resources necessary for sustainability.

The success of traditional Hawaiian civilization depended significantly on the orderly allocation of the water supply, especially for the cultivation of taro. This staple of the Hawaiian diet requires large volumes of cool running water for efficient production. Perennial streams originating in rugged mountains and springs that inundated wetlands were the primary sources of taro irrigation. The Hawaiians built elaborate hydraulic systems, and the rules governing their use evolved as society progressed.

Ancient Hawaiians developed a number of perennial streams with diversions and ditches to irrigate and grow taro. Later, sugar growers copied the ancient Hawaiians with their own elaborate and extensive plantation irrigation systems. The use of intake structures to divert perennial low flows and high storm flows, and the use of water-development tunnels to intercept the high-level ground water associated with perennial streams, ultimately gave rise in the late 1800s to the construction of large scale irrigation systems by sugar plantations.

Miles of ditches, tunnels, flumes, and siphons were constructed to transport water primarily to irrigate sugarcane grown on distant arable lands. This transport was all done without the use of fossil fuel pumping. The Wailua network carried an average 150 million gallons per day without any pumping. Most of these irrigation systems are no longer in use for sugarcane farming. The book Sugar Water, Hawaii's Plantation Ditches by Carol Wilcox covers this history well.

The natural movement of flowing water contains an amount of kinetic energy that can be converted to electrical energy. this is emission and by-product free, sustainable, predictable, and indigenously sourced energy. New turbine technologies are enabling effective energy recovery from natural flows of streams and rivers. Hydrokinetic (in-stream) power generation offers the opportunity to utilize generating resources without the need to construct dams or other impounds. The capture of the hydrokinetic energy in the old plantation ditches, flumes and tunnels has not been attempted on a utility scale.

Water conservation by consumers eliminates all of the “upstream” energy required to bring the water to the point of end use, as well as all of the “downstream” energy that would otherwise be spent to treat and dispose of this water. The best way for increasing water efficiency is to reduce the use of drinkable water for non-consumption purposes. There are two ways to do this: collect rainwater and reuse indoor wash water. The rain that falls on the roof should, if used innovatively, be sufficient for the majority of home uses, including gardening. Rainwater harvesting can be supplemented by treatment of gray water (wash water from the bathroom, laundry, and kitchen) e.g., through gravel reed beds for subsequent use in the garden.

Even backwater (from the toilet) can be treated and re-used on site in some circumstances, or a waterless composting toilet can be installed to ensure water goes to more productive uses. Closing the nutrient cycle, from human waste to fertile, food-producing soil is, in the long term, one of the most critical factors in the sustainability of our population. Our food supply is a vulnerable link between the environment and the economy. While the use of oil dominates the production end of the food system, electricity dominates the consumption end. The oil-intensive modern food system that evolved when oil was cheap will not survive as it is now structured with higher energy prices. We will not be able to continue to import 90% of our food. Most of us will have to grow at least some of our own food.

Among the principal adjustments will be movement down the food chain as we react to rising food prices by buying fewer high-cost imported foods and livestock products. The economic benefits of expanding urban agriculture will become much more obvious. The Water Department’s policy of not supporting agriculture must be changed. If we are to feed ourselves we must expand our water use with “victory gardens” in every yard, park, school, and diversified agriculture on all prime land. The irrigation systems associated with the now closed plantations are available for conversion into supplying irrigation water for diversified agriculture farming.

The Water Department must take a leadership position in working with DLNR and the Department of Agriculture to insure both our water and our food. I sincerely believe that we should be using the still affordable fossil energy that we have, to invest in infrastructure that requires very low energy to run (e.g. gravity flow). We need to rapidly reduce our dependence on off-island sources.

We need to replace systems that are inherently limited by available imported energy (e.g. groundwater pumping). Aggressive restructuring of the system for resiliency and energy efficiency and purchases of renewable energy systems are powerful steps that can be taken to improve our water security while combating global warming. We could all learn from how the Hawaiians and the early plantations operated. These necessary steps to save finite fossil fuel resources and finite biosphere must be done soon.

Business-as-usual will can only lead to there being no water in the pipes and most people unable to live in their homes. You have a choice, support David Craddick's efforts to restructure the water system to gravity flow or plan on moving.

See also:
Water - The Uncertain Resource - Part One http://www.minnpost.com/stories/2009/10/07/12268/noted_lecturers_grapple_with_water_the_uncertain_resource

Water - The Uncertain Resource - Part Two http://www.minnpost.com/craigbowron/2009/10/08/12314/uncertain_resource_do_we_have_a_water_crisis_or_a_crisis_of_water_management

Ea O Ka Aina: Our Water Footprint
8/27/09
Ea O Ka Aina: Water, Water, Everywhere 2/10/09
Ea O Ka Aina: Kauai Water & Power 1/4/09

1 comment :

Post a Comment