Recharging Groundwater with Water-Harvesting Ditches

swales in colorado

“Simply put, swales are water-harvesting ditches, built on the contour of a landscape. Most ditches are designed to move water away from an area, so the bottom of the ditch is built on a modest slope, usually between 200:1 to 400:1. Swales, however, are flat on the bottom because they’re designed to do the opposite; they slow water down to a standstill, eliminate erosion, infiltrate the surrounding area with water, and recharge the groundwater table. When water moves along the flat bottom of a swale, it fills it up like a bathtub — that is, all parts of the bath tub fill at the same rate. The water in a swale is therefore passive; it doesn’t flow the way it would on a slope.” [Read more…]

Water Johads: A Low-Tech Alternative to Mega-Dams in India

water johad india

When the British colonized India, they imposed their own system of water management, which included the building of large-scale dams, sewers, and irrigation channels. This high-tech approach continues today, as the World Bank is urging India to build enormous dam projects to fight drought and depleted aquifers. The Indian government has followed its advice. Its first Prime Minister, Jawaharlal Nehru, called dams the “Temples of modern India”. Since then, India has built over 5,000 dams and large reservoirs. [1]

However, before the British arrived, people on the subcontinent used traditional low-cost, low-tech engineering to collect rainwater for thousands of years. This involved the placement of thousands of small structures throughout rural areas which, in one way or another, catch excess rainwater from the monsoon months and allow it to slowly percolate into the groundwater during the dry season. To maintain and manage these structures, community-based management schemes were necessary. However, these were actively discouraged during British rule and following independence. As a result, in the 20th century many of these small reservoirs fell into disrepair.

[Read more…]

Precolumbian Causeways and Canals

precolombian causeways

Detail of an engineered landscape in the Bolivian Amazon. Artwork by Clark Erickson.

“In contrast to the Western obsession to drain what are considered marginal wetlands for agriculture, farmers in the Bolivian Amazon may have intentionally expanded wetlands and wetland productivity through earthwork construction, which impedes, rather than enhances, drainage. The precolumbian farmers did not use causeways as dikes to prevent inundation of fields and settlements, but rather to expand and enhance inundation for agricultural production. At the same time, impounding water with well-placed causeways and the creation of canals improved and extended the season of transportation by canoe across the landscape. The grid-like structure also permanently marked land tenure in a highly visible manner.” [Read more…]

Think Outside the Bowl

Think outside the bowl

DIY Glaciers: a Low-Cost Alternative to Dams

DIY glaciers“A remote Indian village is responding to global warming-induced water shortages by creating large masses of ice to get through the dry spring months. People in Skara and surrounding villages survive by growing crops such as barley for their own consumption and for sale in neighboring towns. In the past, water for the crops came from meltwater originating in glaciers high in the Himalaya. But in recent decades, climate change has uncoupled glacial melt cycles in the Tibetan Plateau from the traditional agricultural season, causing water shortages in April and May when Ladakhis typically begin sowing seeds for the summer season.”

“One winter in the late 1980s, an engineer from Skara named Chewang Norphel came up with a possible solution to his village’s problem while strolling around his backyard. Norphel noticed that a small stream had frozen solid under the shade of a poplar grove, though it flowed freely elsewhere in his sunny yard. The reason for this, he realized, was that the flowing water was moving too quickly to freeze, while the sluggish trickle of water beneath the grove was not. Over the next several years, Norphel worked to create an irrigation system that functioned using the same simple natural principle. The result has been Ladakh’s artificial glaciers. Ten
have been built to date.”

Read more: Artificial Glaciers Water Crops in Indian Highlands.

How to Build a Spiral Pump

spiral pump

“A spiral pump, first invented in 1746, has been recreated and tested at Windfarm Museum using lightweight and inexpensive modern materials. A 6 foot diameter wheel with 160 feet of 1-1/4 inch inside diameter flexible polyethylene pipe is able to pump 3,900 gallons of water per day to a 40 foot head with a peripheral speed of 3 feet per second.

With its low torque requirements, the pump is particularly suited to be mounted on and driven by a paddle wheel in a current of two feet per second or greater. This easily built, low maintenance spiral pump can be used to provide water without the need for fuel wherever there is a flowing stream or river. It can also be hand turned or otherwise driven to provide a low cost, efficient pump.”

Read more: 1 / 2 / 3 / 4. Thanks to Paul Nash.

See also: