THE FACTS ON LA MANZ. WATER

THE FACTS ON LA MANZ. WATER
Posted by Dave Collins on April 30, 2008, 10:25 am

The following is a summary on the water situation in La Manzanilla written recently by Mark Cable Rains, Assistant Professor of Ecohydrology, Department of Geology, University of South Florida. Mark is part of a research team headed by the Great Basin Institute who has been conducting environmental research in the greater La Manzanilla area since 2001. I have translated this information and am passing it on to Morgan, our water master. Further questions about these issues can be directed to Mark at: mrains@cas.usf.edu

There are four major water-supply wells in La Manzanilla. Two of these wells are owned and operated by La Manzanilla, while two of these wells are owned and operated by Tamarindo. When wells are pumped, groundwater levels drop and groundwater flows towards the wells from all directions. This is not a problem if the wells are located in a large basin filled with fresh water. This can be a problem, however, if the wells are located in a small basin close to the coast, because salt water from the ocean and/or lagoons and mangroves at the edge of the ocean can flow into the aquifer and eventually into the wells. This can become a bigger problem if groundwater pumping is increased. We call this salt-water intrusion, and it is a problem throughout the world in coastal communities that rely on groundwater for their water-supply needs.

Salt-water intrusion may be occurring in La Manzanilla. I emphasize the use of the word "may", because our results are preliminary and have not been fully explored. The background salinity of water in the aquifer is approximately 0.5, while the background salinity of the ocean is approximately 35. The salinity in the primary water-supply well for La Manzanilla was approximately 0.5 in January 2007 and January 2008. However, the salinity in the secondary water-supply well for La Manzanilla, which is closer to the mangrove and closer to the water-supply wells for Tamarindo, was greater than 1.0 in January 2007 and greater than 2.5 in January 2008. These higher salinities may be due to salt-water intrusion, and this increase in salinity may be due to increasing salt-water intrusion. Again, I emphasize the use of the word "may", because our results are preliminary and have not been fully explored. Nevertheless, these results suggest that our work on this issue is timely and necessary if we are maintain clean water for the community of La Manzanilla. In this regard, we are continuing our work and are regularly communicating with Morgan to ensure that he has current information about the La Manzanilla water resources.

Water concerns for La Manzanilla

The post about water concerns below was posted in response to yet another investment and development scheme for the already over taxed water system in the area and generally the Costalegre

Working on the concept of a developement project wich includes condomminiums, swimming pool, restaurant/bar, motel, store and horse back riding facilites.

Just catching up on the latest postings... I think the issue of water comes in here, when any development plans are afoot. What Silver and the rest of us are experiencing is the salt water intrusion into our coastal aquifer.(Morgan told me and others this just a week ago) The salt water is heavier, and sits below the fresh. After all the dry months, the level goes lower and lower, hence the water gets saltier. When we over use the resource it means we draw more salt water into the aquifer, and make the situation worse. LA has the same problem, but they have figured out the capacity of their aquifer, and try to be super careful not to start drawing in salt water. We don't know the capacity here, but we're certainly getting some classic signals. Some months we are right at the legal limit of salinity, according to Morgan.(and more chlorine = more salinity 'cus it comes as a salt)

So, these are things to consider when making investments...if there are few enforceable rules, then certainly many new investors will drain our water resource and jeopardize the well being of the community. Profit and employment are only two of many considerations here. This ecosystem has been supplying us all with water for free, more or less. If we look after it, it will continue to do this forever. This is a good investment! Will we all have to pay big bucks for desalination, because no one makes us accountable for our use of water and we can't adjust to the capacity of our aquifer? Let's look after what we were given, and pass it on in good shape!

Perhaps we and the other stakeholders, including El Tamarindo and Yellowstone Club should find out the capacity of this aquifer. This might go a ways toward all of us reassessing just what we do with water.

There's lots of good stuff on salt water intrusion on the internet...the problem is common.

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