Tuesday, August 14, 2012

La Paz Water and Rainfall

After reviewing a few resources I have compiled the following information about rainfall and water in La Paz and across Baja California Sur, Mexico.

Rainfall Statistics

They show that La Paz receives on average 6.7 inches of rainfall per year.  With the rainiest months being August and September, with 1.2 and 1.4 inches of rainfall on average.

February and December are also notibly "high" months for rainfall with 1.1 inches of rainfall per month each.

March to May being the driest with 0 inches of rainfall on average.

At first view these numbers do not seem accurate as a hurricane in August or September (typical hurricane months in La Paz) bring in much more rain than a small rain in February or December.  This is caused by consistency.  February and December see small amounts of rain every year, at least once, whilst August and September can go a number of years with next to no rain, only to receive up to 6 inches all in one downpour during a large hurricane.

These statistics, as shown in the graph below, are recorded at the La Paz airport.  Typically this area receives rainfall in line with the city itself, however temperatures recorded here can be a few degrees cooler than the city (based on personal experience).

La Paz Water

These rainfall statistics are not, however, a reflection of the rainfall which is experienced in the mountains surrounding La Paz.  Therefore they are not a true reflection of the water situation in the city.

Due to the design of La Paz, your eyes are typically directed towards the Sea of Cortez, however if you cast your eyes behind the city, or use google maps, you will see a large range of mountains, which experience significantly more rain than the city.

The satellite image below clearly shows the vegetation differences in the lower half of Baja California Sur.

Sierra de la Laguna

The largest and darkest green areas of this map, cover approx. 1,000 square miles, are known as Sierra de Laguna (Literally translated as Saw Lagoon).

"The area holds an eclectic mix of landscapes. The mountains provide a rugged home for an incredible diversity of animal and plant life. It is an ecological treasure house where cacti, palms and pine trees grow side by side and rock pools form underneath towering granite boulders.

The dry forests of Sierra de la Laguna are home to some 224 species of plants, half the reptiles and amphibians in the entire Cape Region(the land to the east of the mountains is known as the Cape or the East Cape), and 96 percent of the region's mammals.

The highest elevations of the Sierra de la Laguna are blanketed in pine-oak forests, merging with tropical dry forest at about 2600 ft. in elevation.

At about 950 ft. in the Cape region the tropical dry forest gives way to the Sonoran Desert. During the long dry season of this eco-region, many of the trees loose their leaves".
Extract from summitpost.org

Canyons of the Sierra de la Laguna 2
Canyons of the Sierra de la Laguna 2
The photographs below show the impact of regular rain on the geography and the plant life. For more information on Sierra de la Laguna in particular and visiting this region please visit Summit Post's website.

San Juan de los Planes - Water Basin

Closer to La Paz is a smaller mountain and hill range, which although not as high and large as Sierra de la Laguna, still provides a large water run off on a regular basis.

Fortunately for La Paz this run off does not take place straight into La Paz, and in fact runs off to the other side of the mountain range into an area known as San Juan de los Planes.  Many know of this area as it is on the drive to El Sargento and La Ventana, as well as Bahia de los Suenos (or Muertos).

The satellite imagery below shows clearly the mountain run off from the hills just behind La Paz.  Out of the 12 large, and clearly visible, river beds only one feeds into La Paz, and this is predominantly only flowing during hurricane seasons.

The remaining 11 river beds feed from the large hill top and mountain areas surrounding them, and they subsequently deposit their water into San Juan de Los Planes.  This area as you may be able to make out from the imagery is largely an agricultural area supported by the rainfall run off.

To be continued...

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