Water & Landsat’s Thermal Band

Irrigation: a numerical explanation

Irrigation accounts for 80% of fresh water use in the U.S and worldwide, the World Bank estimates 70% of fresh water use is for agriculture. The U.S. irrigates over 50 million acres of agricultural land and 32 million acres of recreational landscapes (lawns, golf courses, etc.). The total volume consumed by agriculture and landscape irrigation is 50 trillion gallons per year; western states are responsible for86% of that consumption

Irrigation system in Colorado. Photo credit: USDA

 National Resources Conservation Service

A growing problem

The arid U.S. West is experiencing explosive population growth. The 2000 Census reported that one third of all Americans live in the West, and that the West accounted for half of the overall U.S. population growth over that decade

Seven of the ten fastest growing U.S. cities are found in the West and Albuquerque, El Paso, Las Vegas, and Tucson will not be able to supply enough water for their burgeoning growth with present sources. Recent drought brought about bitter legal battles for the precious water resources of the Rio Grande River highlighting that the river’s waters are stretched thin between the city of Albuquerque, farmers, endangered species, and local Native Americans.

As the West grows, water conservation is coming to the forefront. Water 2025 states, “today’s water supply issues require innovative, locally based approaches that identify solutions in advance of water supply crises

New FAO publication aims to bring small-scale irrigation to farmers in sub-Saharan Africa

Irrigation is a key tool for agricultural intensification. Although only 16 percent of the world's fields are irrigated, they yield 36 percent of global harvests. In developing countries, irrigation increases yields of most crops by 100 to 400 percent. Despite this, some of the world's most needy farmers are still unable to water their land effectively

The use of porous jars buried up to the neck is one of the oldest irrigation methods and is practised by traditional farmers throughout North Africa and the Near East

Professor Daniel Hillel, expert in soil/water relations, was asked by FAO Director-General Jacques Diouf to write an irrigation book specifically for one major group of vulnerable agriculturists - the small-scale farmers of sub-Saharan Africa. Hillel is irrigation advisor to the Oversight Committee for FAO's Special Programme on Food Security, spearhead of the Organization's work to promote food self-sufficiency in the world's poorest countries. As a retiree, he was contracted under FAO's Programme for the use of retired experts

"Small-scale irrigation for arid zones: Principles and options" promotes HELPFUL (High-frequency, Efficient, Low-volume, Partial-area, Farm-Unit, Low-cost) irrigation techniques. Hillel, who has a lifetime's experience of irrigation, points out that "Elaborate and expensive systems ... imported and installed in the grand hope of achieving instant modernization, typically fail for lack of expert maintenance and spare parts. Such installations can quickly become white elephants - idle monuments to hasty 'progress' relying on ill-adapted technology."

When they do work, poorly managed irrigation systems cause a range of environmental problems. Rising water tables, caused by excessive applications, leakage from drainage channels and inadequate drainage, lead to salinization and waterlogging, which reduces crop yields. Conversely, overpumping of groundwater depletes supplies and threatens long-term viability of the irrigation schemes and the crop yields they support

Irrigation

Irrigation is an artificial application of water to the soil, usually to assist with the growth of crops. In crop production, it is mainly used in dry areas and in periods of rainfall shortfalls, but also to protect plants against frost. Additionally, irrigation helps suppress weed growing in rice fields. By contrast, agriculture that relies only on direct rainfall is referred to as rain-fed farming. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given area

Irrigation is also a term used in the medical/dental fields and refers to flushing and washing out anything with water or another liquid. This article focuses on irrigation of the soil for agricultural purpose

Gated Irrigation 

  Polyethylene Gated Pipe Irrigation Systems

I took the above photo of a modern “gated pipe irrigation system” being used on a high altitude ranch on the West slope of Colorado last weekend. This new gated polyethylene pipe replaced older aluminum gated pipe which was being stored elsewhere on the property. It can also be used to replace earthen ditches, eliminating ditch leakage. The system is set up by delivering water into the pipe using a concrete box containing a tight screen or filter which keeps debris out of the water entering the pipe. Pipes may range from four inches to 15 inches in diameter. Every two feet, the pipe has a plastic slide, or “gate” that can be opened or closed using an irrigating “shovel”. Each gate opening is a rectangle that is a few inches wide. This is a form of flood irrigation, or gravity irrigation. There are NRCS (Natural Resources Conservation Service) government programs available to help pay to upgrade older ditch systems to this more efficient method

 Groundwater, Running on Empty

Earth's underground aquifers are at risk of being sucked dry

Efficient irrigation practices may help ease the pressure on groundwater resources

 

The underground aquifers that store more than 90 percent of Earth's liquid freshwater are at risk of being sucked dry. A study published in Nature in August showed that annual demand from the world's 783 large regional aquifers is 3.5 times the amount that is replenished. The impact could be profound: Groundwater sustains nearly 2 billion people and provides almost 40 percent of crop irrigation worldwide. Tom Gleeson, a hydrologist at McGill University, calculated each major aquifer's footprint the area needed to sustain its use and compared that with the actual size of the aquifer. "In many of the places where the footprint is larger than the aquifer, we are unsustainably mining groundwater," he says. Gleeson suggests switching to more water-efficient farming in India, Pakistan, Saudi Arabia, Iran, Mexico, and the United States, countries that are overtaxing their groundwater supplies the most

What are some effects of ground-water depletion?

If intensive pumping from an aquifer continues, then adverse effects may occur.Water-well problems Declining ground-water levels have three main effects on water wells. First, as the depth to water increases, the water must be lifted higher to reach the land surface. As the lift distance increases, so does the energy required to drive the pump. Thus, power costs increase as ground-water levels decline. Depending on the use of the water and the energy costs, it may no longer be economically feasible to use water for a given purpose. Second, ground-water levels may decline below the bottom of existing pumps, necessitating the expense of lowering the pump, deepening the well, or drilling a deeper replacement well. Third, the yield of the well may decline below usable rates.

Overview of groundwater

Water is recharged to the groundwater system by percolation of water from precipitation and then flows to the stream through the groundwater system.

Water pumped from the groundwater system causes the water table to lower and alters the direction of groundwater movement. Some water that flowed to the stream no longer does so and some water may be drawn in from the stream into the groundwater system, thereby reducing the amount of streamflow.

Water-level declines may affect the environment for plants and animals. For example, plants in the riparian zone that grew because of the close proximity of the water table to the land surface may not survive as the depth to water increases. The environment for fish and other aquatic species also may be altered as the stream level drops.