by Jerry J. Toman, ScM, ChE
This, the second article in the series The Two-Headed Dragon–Energy/Water/Food Scarcity and Climate Change — the Top Ten Policies that Feed It; Two New Technologies (and One Old) that Could Enable us to Slay It and Save the Planet focuses on the unintended side effects of large dams and levee systems. It specifically discusses how they are causing serious environmental problems downstream that are becoming more damaging than the benefits that these dams and levee systems provide. In many ways this cautionary tale is applicable to many other technological and large scale engineering interventions into natural systems, especially when these technologies and engineered systems are not well understood.
Nature Has Engineered an Exquisite System and We Are Messing With It
Nature has built sustainable and natural ecosystems based on rainfall falling over a watershed, which, in many cases, falls most abundantly in the headwaters. The water head developed is released by gravity flow through naturally carved channels, occasionally being retained in natural depressions, forming lakes. The flow eventually reaches the sea or some large inland lake (e.g. Volga into the Caspian Sea). Rock weathering creates silt, which is carried with the water, some of which is deposited in the river bed. When flows are exceptionally large, the water scours up these minerals in some areas, and carries it over the banks in others, providing trace-mineral fertilization over large land areas adjacent to the river.
Due to natural global weather cycles and oscillations (e.g., that responsible for “El Nino”) the rainfall for a particular watershed may vary considerably from year to year, or even over decade-long events. But for the most part, even with variations, it can be counted upon to preserve an ecosystem of a particular type over periods which may extend from a few thousand up to millions of years.
Cheap Fossil Energy Fueled the Building of Large Dams; We Are Now Seeing the Consequences
Since the discovery of coal, and more significantly, that of petroleum, including methods of refining it into fuels that power engines contained in large, earth-moving machines, we have developed the capability and penchant of significantly modifying these large hydraulic systems.
The most ambitious of these projects has been the High Aswan Dam in Egypt, at least until recently where its scope may be matched by the “Three Gorges Dam” in China. This project has altered not only the nature of the Nile river, and its fertile basin, but Egypt itself, including upstream countries, as well as the health of the Mediterranean Sea.
While there were obvious immediate benefits of the project, it is becoming increasingly evident that, in the long-run, the costs either have become or will soon become, greater than the benefits. A full discussion of the positive and negative effects of this project is beyond the scope of this article—a good one — can be found at: You Hide, O Gift of the Nile
Our Own Mississippi Blues
Closer to home, we have seen the sad decline of the Mississippi River Basin. The rich topsoil in the enclosed region used to be two feet thick or more, but now it is barely 6 inches. Now, instead of silt, which used to overflow the banks of the river to enrich farmland, the levees constructed forces the river carry to carry toxic chemicals from farm run-off, including pesticides, all the way to the Gulf of Mexico, creating huge dead-zones in the Gulf and beyond. To this devastation, the loss of thousands of protective acreage and bayous south of New Orleans has to be added and noted.
The reclamation of land from the sea by The Netherlands might be cited as an exception where the benefits accrued have been substantial (so far, so good). One might also cite the Electric Plant at Niagara as a project where more good than harm has been created. This did not involve a building a new dam, however, since it used a natural one, and the watercourse altered is a short one, connecting two of the Great Lakes.
Problems with Dams in the Tropics
Dams built in tropical or subtropical regions tend to have the greatest overall negative effect, often inundating large areas causing putrefaction of the rich vegetation. A horrific example of such destruction, which benefitted primarily international aluminum smelting companies, providing little benefit to the general population, is that of the Tucurui Project in Brazil. This is described by Philip M. Fearnside of the National Institute for Research in the Amazon. (Ref: Environmental Impacts of Brazil’s Tucuruı´ Dam: Unlearned Lessons for Hydroelectric Development in Amazonia).
Currently the government of Brazil is planning to build an even larger dam on the country’s second largest river, the Madeira, at Belo Monte. Activists in Brazil as well as the rest of the world need to stop this project in its tracks. If not suspended, not only will the local ecosystem be damaged, but decaying vegetation will release carbon heretofore sequestered in the biomass. The world-wide warming problem by carbon dioxide released into the air will be exacerbated, with de-alkalization of the oceans by the same chemical causing additional collateral damage, which probably will be irreversible.
Convective Available Potential Energy (CAPE)
Although the people of Brazil are not aware of it, their country has a bounteous supply of Convective Available Potential Energy (CAPE). This form of residual solar energy is convertible to electrical energy using new technology without incurring the environmental destruction of a new dam. (Part IV). As a bonus, the new technology would perform like thousands of trees, at least with regard to their transpiration function, reversing the trend towards the drying of the regions climate at the fringes.
Some Final Examples of Dam Problems
There are numerous other examples throughout the world of dams and comprehensive water projects that were approved in the “old technology” era, including the Three Gorges Dam in China, the long-functioning Colorado River development, which of late, has been losing growing fractions of its flow to evaporation. In a recent study by Martin J. Pasqualetti and Scott Kelly of Arizona State University, it was estimated that evaporation losses from the lakes behind the hydroelectric dams on the Colorado River corresponded to as much as 56,000 gallons per MWhr of electricity generated as compared to a mere 765 gal/MWhr for nuclear power, and 800 to 1000 gal/MWhr for solar thermal in California.
Finally, California’s Central Valley Water Project, is now observed to have gone terribly wrong in the midst of persistent drought. Californians now face the terrible dilemma of either suspending the pumping of water from the Delta at the confluence of the San Joaquin-Sacramento River to the south for agricultural purposes, or continuing this practice and destroy what’s left the Delta ecosystem. In Part IV, the possible reversing of the damage within a few decades by adopting a strategy involving the deployment of new technologies will be proposed.
© 2009, Jerry_Toman. All rights reserved. Do not republish.