New Mexico's Acequias: Irrigation and Social Organization

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Social stability is the last but perhaps the most important of irrigation's "3s", for without adequate social organization and long term stability, irrigation is impossible. In the United States a variety of cooperative, local, state and federal agencies act to provide the necessary social organization for water management, with the Federal Bureau of Reclamation the best known and largest entity. That federal agency has been responsible for the development and maintenance of a series of huge projects in the western United States including the Colorado River projects, the Columbia Basin Project and parts of California's complicated water management system. All of those systems have venerable ancestries. Immense irrigation projects under centralized control were known to the ancient societies of Mesopotamia, while small and locally controlled irrigation projects date to long before the beginnings of recorded history in all arid and semi-arid parts of the world where agriculture has been practiced.

The state of New Mexico, one of the longest European settled parts of the United States, has a tradition of irrigated agriculture stretching back well before the first European contact. With parts of the Colorado River projects and large ones along the Rio Grande (Rio Bravo del Norte) New Mexico is something of a microcosm of virtually all of the types of irrigation water control known in the western United States. It also has some of the more complicated water laws, for it is a mostly arid state but also has high mountains where melting winter snows are the sources of exotic rivers, most notably the Rio Grande and its largest tributary the Pecos. Allocation of that water is a complicated task, a task made increasingly difficult by drought years when mountain show is scarce. In addition to dividing water between users who live within its boundaries, New Mexico is obligated to send water to downstream users on the Rio Grande, the Pecos and several smaller streams into Texas and Mexico (and in a less complicated set of relations to downstream users on the Colorado - New Mexican users of water destined for the Colorado are few in number).

Snow in New Mexico, 16 March 2005

source: NASA Earth Observatory

Acequias in New Mexico (with a few also in Colorado) are numerous, almost 1,000 of the gravity driven channels bring water from highland areas for use in towns and agricultural plots. They are also very old, brought to the area by settlers from Mexico and Spain who were familiar with community operated irrigation first in Spain and later in New Spain (Mexico). Some of the canals themselves may actually date to pre-contact groups, for acequias use an ancient technology widespread where snowmelt in nearby mountains allows agriculture on downhill sites. The social organization in pre-contact groups is for the most part unknown, and some of the current aspects of acequia management may have roots there, but the acequia associations are quite similar in character to much older ones in México and in Spain.

While ancien regime Spain and its colonies were not in the remotest sense of the term democratic in almost all aspects of governance, acequia associations were participatory democracy in its most pristine form. Yearly or more often those who had a share in the water delivered by an acequia met, a mayordomo (ditch boss) or leader was chosen, and both the allocation of water and of tasks necessary to keep the channels open, free of silt and debris, were made by common consent. A kind of corvée was in effect, for peasants were compelled to spend time working on the channels, but instead of working for benefit of the state or the nobility as in other corvée, they were working for the common good of their local community and for personal benefit.

The acequia associations of contemporary New Mexico share that characteristic of participatory democracy (no, New England town meetings are not the only example of direct democracy in the United States). For the past several decades the associations have become legal entities and an integral element in the management of water in New Mexico. Beneficiaries of the water are compelled to participate in the maintenance of the ditches, and in years of drought they must make the difficult decisions on how to allocate the scarce resource.

Folr a fascinating look at acequias and the experience of being a ditch boss in New Mexico, see Stanley Crawford's Mayordomo: Chronicle of an Acequia in Northern New Mexico.

Notes IV: Global Water Magazine

Washington Monument, Mt. Vernon Square, Baltimore, MD

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Material seems to be coming at me faster than I can pull it into some kind of coherence. I had planned next to put up a posting about acequias and the water laws of New Mexico, but this morning the estimable blog Waterwired pointed me toward a new online publication available free from the Global Water Program at Johns Hopkins University, Global Water Magazine. The Baltimore university is a suitable venue for the magazine. Its medical school is world famous, but the university also has strengths in many other areas related to water and water management. The first true research university in the United States, the first president of Johns Hopkins was the geographer Daniel Coit Gilman (who had earlier served as president of the University of California, my Ph.D. alma mater). Under the father and son Wolman, its Geography and Environmental Engineering program was one of the preeminent places in the United States for the study of physical geography and water related problems. More recently its Global Water Program has brought together scholars from a number of disciplines to study all kinds of issues related to water. The first issue of the magazine is engaging, and the publication promises to become an important intermediary between scientific research on water issues and the public. RECOMMENDED!

Notes III

Carhenge, Alliance, Nebraska

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In the posting about dams, I failed to note one major issue, the possibility of failure. Well-engineered dams rarely fail, but poor engineering, extreme weather events and lack of proper maintenance can lead to failures. In a few cases so can bad water management as illustrated by the first pages in Powell's Dead Pool, where the author describes what could have been a catastrophic failure of Glen Canyon Dam on the Colorado River.  Under the worst of circumstances, a catastrophic failure can lead to hundreds or even thousands of casualties. The most famous dam failure in the United States was at Johnstown, PA in 1889 when a badly maintained dam broke and killed 2,200 people. (That same benighted city had further floods in 1936 and again in 1977, devastating to property but not nearly as deadly for people, and neither was the consequence of a dam failure but rather of extreme weather.) Two days ago a small dam in Iowa collapsed after torrential rains. Knowing the failure was likely, deaths were apparently avoided, but several downstream towns had to be evacuated, and there was substantial property damage.

The St. Francis Dam, a water supply dam built in the early 1920s and designed by the famed California water engineer William  Mulholland, catastrophically failed on 12 March 1928 due to an engineering error. The ensuing flood killed 450 people and washed away towns and farms in the Santa Clarita Valley NW of Los Angeles.  Another badly engineered dam failure was the collapse of the irrigation retention  Teton Dam in Idaho in 1976 leading to 11 deaths and tremendous property damage downstream (see some pictures of the collapse on the website of a civil engineering faculty member at San Diego State University. Driving through the area later that summer, I stopped in Rexburg, Idaho to witness some of the devastation, but I have not scanned my slides as yet).

Shortly after posting the piece on glaciers yesterday, I read the New York Times (NYT) Sunday 25 July issue. While I am no fan of their regular columnist Thomas Friedmann,  he has an interesting op-ed  on global warming worth a read. This has been one of the hottest summers ever recorded in the eastern United States, and if current trends continue it could be the hottest yet recorded. Despite that heat (which it must be noted may be completely unrelated to climate change) the Senate has killed even the feeble climate legislation pending before it. Perhaps that is all to the well, for sometimes half measures like those in the bill now dead are worse than no action at all, but the lack of attention to the matter of climate change and the overuse of petroleum products in a hot summer with the Gulf oil gusher only temporarily capped is quite disturbing. It would seem those topics should be the subject of a national frenzy and demand for action. This morning's NYT has a good piece by their regular columnist and Nobel laureate Paul Krugman bemoaning the Senate's action, or or more exactly their lack of action placing a substantial share of the blame on the unprincipled ex-presidential candidate McCain and showing how the demands of the coal and petroleum oligopolies have trumped the public interest.

More water woes in the DC area. The drought may have broken for a time with heavy rains and strong winds accompanying a thunderstorm yesterday afternoon. The storm led to numerous electrical supply problems, and one facility loosing power was a major filtration facility of the Washington Suburban Sanitary Commission causing it to once again issue mandatory water usage limitations for Montgomery and Prince Georges Counties. While water supply systems are often discussed in the abstract and without reference to other elements of urban infrastructure, storms and other catastrophic events illustrate how interdependent those elements are.

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Climate Change - Glacial Retreat

Receding glacier, Upper Joffre Lake, British Columbia, Canada

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Any discussion of world water supplies over the next century must take into account climate change or what is frequently termed "global warming." The scientific consensus has long since concluded that an increase in global temperatures of several degrees over the next century is nearly certain. The only remaining debate is on how great and how fast the warming will be. That is an important debate, but a little outside our purview. What is important is the impact of increased temperatures on world water supplies. The worst case scenarios for that issue are, to use a very bad pun, chilling indeed.

One early sign of the increase in global temperatures is the recession of glacial ice in the Northern Hemisphere and of mountain glaciers in tropical areas. Glaciers are an important part of the water supply equation as well as a key variable in world climates. Glacial ice acts as a natural reservoir helping to keep runoff in streams constant over the year and from wet years to dry ones. Many perennial streams would run dry for several months a year, and for several years in succession in a severe drought, were it not for glacial melt. Exotic rivers in North America and Asia depend on glacial melt for a sizable part of their flow. The disappearing glaciers of the Rockies are major suppliers of water to the great American Rivers of the west. As a sad example, Glacier National Park is rapidly loosing its namesake features and may have no glacial ice in less than a century. In the Coast Range of British Columbia many glaciers are rapidly melting, like the one feeding Joffre Lakes, one of the most stunning sets of glacial lakes in the world. Not long ago that glacier reached the water of the upper lake. Now the melting glacier is more than 100 meters higher than the lake surface.

Highland glaciers are found in several tropical areas where there is clear evidence of rapid melting. Much of highland tropical South America, including populated parts of Ecuador, Peru, and Bolivia, has permanent streams only because of the water released when glaciers in the high mountains melt. Urban water supplies and irrigation are dependent on that water, for the region is characterized by a division between a wet season and a dry season. There is disturbing evidence of glacial retreat in that area as there is in New Guinea. Kilimanjaro has one of the few glaciers in Africa, and the debate is not if the glacier will disappear but when with the best guess being in about 10 years.

Outside the tropics there is rapid glacial melting in the Himalaya. An unfortunate error in a major climate report concerning glacial melting in the Himalayas has been used as "evidence" by those opposed to the idea of global warming, persons who believe, against all evidence, that global warming is a myth being perpetrated by greedy scientists to get more research funding. The elected Attorney General of the antediluvian Commonwealth of ole Virginny is among those anti-scientific Luddites. Almost all of them are slavishly repeating the propaganda generated by the coal and petroleum industry, an industry which does not want to have any limits placed on coal and oil consumption, the major source of the most important greenhouse gas carbon dioxide. It is clear the glaciers are less important as sources of water in major Asian rivers than the report indicated, and the rate of melting is slower than the alarmist information in the report. But glacial melt in the world's highest mountains is crucial to the flow of the Indus and significant in several other streams. The retreat of those glaciers portends catastrophe in an area where water supplies are already seen as inadequate to meet increasing demands.

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Irrigation and Salt

Wind eroded and salt encrusted hoodoos, Atacama Desert, Chile

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For the past several days I have been wracking my memory and rifling my notes to find the first time I encountered the "3 s" of irrigation - silt, salt and [political] stability. The idea is so straightforward that perhaps the term has been around forever, or at least as long as supplemental water has been used to grow crops. Salt and silt threaten the utility of irrigation works and the soils to which water is applied, while political stability is required if irrigation works are to be maintained over time. Irrigation at any significant scale is a cooperative activity requiring many people to participate in the construction and upkeep of the impoundments to store water, the canals to bring it to fields, and the drains to remove excess water and prevent water-logging of soils. Archaeology and history provide numerous examples of cases where irrigation systems fell into disrepair because soils became too saline for use, because impoundments and canals were clogged with silt, or because political unrest made it impossible to maintain the irrigation works. On occasion the destruction of irrigation works has been a deliberate ploy in warfare as an enemy attempts to starve a population by destroying its agriculture.

Silting behind large dams was noted in the posting on immense dams. It is also a problem behind even the smallest hydraulic barriers and unless water is moving rapidly, it can be a problem in canals as well. In a later posting we shall examine that idea in a bit more detail. In later postings and in the lectures we shall also examine the importance of political stability in the maintenance of irrigation systems.

Today I would like to make a few comments about salt as an enemy of irrigation projects. Salinization is a complex problem for all water systems. Many mineral salts, including the most important single one NaCl or sodium chloride (common table salt), dissolve readily in water. At low concentrations those salts can be be inconsequential or even beneficial for human consumption and agricultural use. At some level of concentration, however, they become a problem, and beyond some maximum concentration the water is no longer useful. We may look at salts other than NaCl later, but for today let us limit discussion to it.

Crop plants vary greatly in tolerance to saline soils and salty water. Grains and grasses tend to be more tolerant than other field crops, while most tree crops are intolerant of saline conditions. When land is being considered for irrigation, an early test is of the natural salinity of the soil recognizing that high value fruit, vegetable, fiber and tree crops are unlikely to thrive if the soil is already quite saline. Grain crops in general do not return enough value per hectare to justify investment in irrigation facilities.

Salts accumulate in soils through a variety of processes, and some soils are naturally saline, especially ones derived from rock substrates containing high levels of salt. Elsewhere in arid areas evaporation of surface ponds and lakes leads to pockets of salty soil (often called playas in Mexico and the southwestern US  and salinas in South America). Once overlain by glaciers, with numerous small ponds and lakes left as the glaciers receded the now semi-arid southern part of the Canadian province of Alberta, its agricultural area, has salty soils spread quite widely. Some of those soils derive from salty substrates, while other areas were once covered by waters now evaporated away. As grains and grass fed livestock are the primary agricultural products, the presence of salty soil is not a great hindrance to agriculture in Alberta (uncolored areas on the map are generally unsuitable for agriculture for other reasons, while blue areas are lakes and streams).

Source: Agriculture Canada and Province of Alberta

Commonly soils become salty after irrigation commences. Not infrequently in arid areas the water used for irrigation is itself  saline. Rainwater dissolves salt as it flows across desert landscapes in infrequent storms. Water captured in impoundments becomes increasingly saline as evaporation occurs. The extremely high rate of evaporation in hot desert areas like those of the southwestern US mean that water leaving Lake Powell or Lake Mead is far saltier than water flowing into those reservoirs. Applied to the soil in areas with high rates of evaporation, some salt from that water is added to the soil with irrigation. Much of the salt is leached to lower levels in the soil profile, and some of that, in turn, is washed away. But water retained in the soil can be  returned to the surface in a capillary process as water is drawn upwards to the soil surface by evaporation.

Rain or irrigation, in the absence of leaching, can bring salts to the surface by capillary action

Source: Wikipedia Media Commons

Only if it is possible to flush the salts by using a large quantity of water to redissolve the salts and thus to remove them can the eventual salinization of the soils be prevented. Accumulation of salt in soils has rendered substantial areas once productive agricultural zones into salty desert too saline for crops. In the Middle East and in arid parts of Asia, many square kilometers of once productive agricultural activity have been abandoned because of salinization. 

Source: Australia Department of Agriculture, Fisheries and Forestry, Bureau of Rural Sciences

While irrigation agriculture is fairly new to Australia, the Murray River Basin in the southeastern quadrant has been irrigated for more than a century. Not surprisingly, that arid area is reporting salinity problems as the map illustrates.

Dams - The Fascination of the Immense

Three Gorges Dam and Reservoir, Yangtze River, China, June 2009

NASA Earth Observatory

Standing on the Nevada shore (being careful not to cross over into Arizona where one might be arrested as an enemy alien) and admiring the sleek arch and art deco works of the great Boulder Dam (aka Hoover Dam) across the Colorado it is difficult not to be awed at the power of humanity. Many years ago a famous architect working on one of the megalomaniac urban design projects for which his field is notorious said something to the effect "make no little plans for they have no power to stir men's blood."  The design project thankfully came to naught, but his statement still has power. Nowhere is that more true than in the construction of huge dams. The icons of the New Deal in the United States are large dams, from the impressive structures on the Tennessee River and its tributaries as a part of the TVA to the grandest two of all, Boulder Dam on the Colorado and Grand Coulée on the Columbia. Subsequently dictators, autocrats, and even a few leaders in nominally democratic states have ordered construction of immense dams including ones on most of Russia's great rivers, on the Nile, on the Paraná, and on China's Yangtze. The dams have been variously designed to prevent flooding, to improve navigation, to store water for irrigation, and to produce electricity, with most of them intended to do at least two of that magic four.

Immense dams have come with a set of problems, however. Blocking the normal flow of the river, they serve also to block the flow of silt, and it collects behind the dams. The Aswan Dams on the Nile have blocked the flow of silt onto Egypt's riverine fields. While they generate a huge amount of electricity, much of that is used to produce fertilizer to take the place of the silt that once made the Nile Valley a breadbasket. Meanwhile the Nile delta is rapidly receding (and Egypt is getting smaller) as it is not receiving silt from upstream. The huge dams on the Colorado in the United States are also rapidly silting, though the low flows of the past decade mean that silting has been slowed. Eventually silting will render the dams useless for water storage and degrade or eliminate their benefits of flood control, navigation, irrigation water storage, and hydroelectric production. All dams are subject to silting, but the problem is especially great on rivers like the Colorado and the Nile whose headwaters include areas of easily eroded materials like sandstone.

A motto of the early Soviet experiment was "socialism plus electricity equals communism," and the construction of immense hydroelectric dams was a key goal throughout the ill-fated Leninist-Stalinist pseudo socialist experiment. A year ago Sayano–Shushenskaya Dam, one of the huge dams in Russia built by the Soviets to produce electricity, experienced a large explosion in its powerhouse, flooding the powerhouse and among other things sending a plume of lubricant oil down the Yenisei toward the Arctic, destroying several turbines, and killing at least 74 people. For a time Russia's electricity supply was reduced by a sizable percentage, and several key export industries, including aluminum production, were harmed. The flooded powerhouse had ot be closed and repaired, a process still ongoing, though the dam is again producing electricity.

Yesterday evening BBC News America had a story on flooding in China, high water on the Yangtze below the world's largest dam. One of the functions of the dam was to prevent downstream flooding, but it would seem it is having almost the opposite result. At least according to Chinese authorities the dam itself, also intended to  is secure  Earlier it was discovered that large dams in China were creating earthquakes and might have been directly responsible for several large and deadly temblors.

One must hope the Three Gorges Dam is the final immense dam built on earth to improve navigation on the Yangtze, to store water for downstream irrigation, and to produce hydroelectricity. Given the predilictions of totalitarian governments that may be a vain hope, but accumulated evidence makes it clear that huge dams create problems far greater than those they are intended to resolve.

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Water and Agriculture: A General Overview

Boh Tea Plantation, Cameron Highlands, Malaysia

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Agriculture is by a considerable measure the largest single human use of water. Leaving animal husbandry aside for the moment, some of the water used by crop plants is taken up directly from soil moisture created by precipitation in what is often called rain fed agriculture. It has become conventional to call that water from precipitation green water (a somewhat unfortunate usage, for the term is also applied to water seriously contaminated with algae). In the humid zone countries of the northern Hemisphere, including the eastern parts of the United States, green water allows a variety of crops to be grown without supplemental irrigation, and precipitation supplies all of the water for the crop plants. Such is the case in the tea growing area in the tropical highlands of Malaysia where tea is but one of a variety of crops grown dependent on the ample rainfall.

Elsewhere agriculture as presently practiced requires the addition of water beyond that provided by precipitation. Water obtained from streams, lakes and underground aquifers is usually termed blue water (again an unfortunate usage, for blue water has a quite different meaning to sailors). In sub-humid zones  irrigation may provide only small amounts of additional water applied at specific times during the growing season. In truly arid areas little or no crop production is possible without continual irrigation throughout the growing season. An area like the Salt River Valley of Arizona would not be useful for agriculture if not for irrigation.  Many other areas in the western United States can be used for water dependent crops only because of irrigation. Without irrigation in those areas, rain-fed agriculture could only produce grains Like wheat and barley.

The map below illustrates blue water withdrawals from various sources like lakes and reservoirs and underground aquifers for agriculture. It illustrates the great importance of supplemental water in tropical and subtropical areas, particularly in the Middle East and Asia. A very large fraction of the world's population depends on food grown with at least some use of blue water in irrigation, including most of the populations of India and China. The data are averages for usage in whole countries from the Food and Agriculture Organization (FAO), a Rome based unit of the United Nations.

Not all water used in agriculture is consumed, that is lost to evapo-transpiration or incorporated in the crop, but a great deal is. The map below composed from remote sensing imagery at the Institut für Physische Geographie (Physical Geographical Institute) of the Johann Wolfgang Goethe University of Frankfurt am Main in Germany shows the consumptive use of blue water by agriculture across the globe. The map is part of a very large project on world irrigation at the institute.