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Figure 4. Topography and Drainage

Panama is located on the narrowest and lowest part of the Isthmus of Panama that links North America and South America. This S-shaped part of the isthmus is situated between 7° and 10° north latitude and 77° and 83° west longitude. Slightly smaller than South Carolina, Panama encompasses approximately 77,082 square kilometers, is 772 kilometers in length, and is between 60 and 177 kilometers in width (see fig. 1).

Panama's two coastlines are referred to as the Caribbean (or Atlantic) and Pacific, rather than the north and south coasts. To the east is Colombia and to the west Costa Rica. Because of the location and contour of the country, directions expressed in terms of the compass are often surprising. For example, a transit of the Panama Canal from the Pacific to the Caribbean involves travel not to the east but to the northwest, and in Panama City the sunrise is to the east over the Pacific.

The country is divided into nine provinces, plus the Comarca de San Blas, which for statistical purposes is treated as part of Colón Province in most official documents. The provincial borders have not changed since they were determined at independence in 1903. The provinces are divided into districts, which in turn are subdivided into sections called corregimientos. Configurations of the corregimientos are changed periodically to accommodate population changes as revealed in the census reports.

The country's two international boundaries, with Colombia and Costa Rica, have been clearly demarcated, and in the late 1980s there were no outstanding disputes. The country claims the seabed of the continental shelf, which has been defined by Panama to extend to the 500-meter submarine contour. In addition, a 1958 law asserts jurisdiction over 12 nautical miles from the coastlines, and in 1968 the government announced a claim to a 200-nautical-mile Exclusive Economic Zone.

The Caribbean coastline is marked by several good natural harbors. However, Cristóbal, at the Caribbean terminus of the canal, had the only important port facilities in the late 1980s. The numerous islands of the Archipiélago de Bocas del Toro, near the Costa Rican border, provide an extensive natural roadstead and shield the banana port of Almirante. The over 350 San Blas Islands, near Colombia, are strung out for more than 160 kilometers along the sheltered Caribbean coastline.

The major port on the Pacific coastline is Balboa. The principal islands are those of the Archipiélago de las Perlas in the middle of the Gulf of Panama, the penal colony on the Isla de Coiba in the Golfo de Chiriquí, and the decorative island of Taboga, a tourist attraction that can be seen from Panama City. In all, there are some 1,000 islands off the Pacific coast.

The Pacific coastal waters are extraordinarily shallow. Depths of 180 meters are reached only outside the perimeters of both the Gulf of Panama and the Golfo de Chiriquí, and wide mud flats extend up to 70 k 1000 kilometers seaward from the coastlines. As a consequence, the tidal range is extreme. A variation of about 70 centimeters between high and low water on the Caribbean coast contrasts sharply with over 700 centimeters on the Pacific coast, and some 130 kilometers up the Río Tuira the range is still over 500 centimeters.

The dominant feature of the country's landform is the central spine of mountains and hills that forms the continental divide (see fig. 4). The divide does not form part of the great mountain chains of North America, and only near the Colombian border are there highlands related to the Andean system of South America. The spine that forms the divide is the highly eroded arch of an uplift from the sea bottom, in which peaks were formed by volcanic intrusions.

The mountain range of the divide is called the Cordillera de Talamanca near the Costa Rican border. Farther east it becomes the Serranía de Tabasará, and the portion of it closer to the lower saddle of the isthmus, where the canal is located, is often called the Sierra de Veraguas. As a whole, the range between Costa Rica and the canal is generally referred to by Panamanian geographers as the Cordillera Central.

The highest point in the country is the Volcán Barú (formerly known as the Volcán de Chiriquí), which rises to almost 3,500 meters. The apex of a highland that includes the nation's richest soil, the Volcán Barú is still referred to as a volcano, although it has been inactive for millennia.

Nearly 500 rivers lace Panama's rugged landscape. Mostly unnavigable, many originate as swift highland streams, meander in valleys, and form coastal deltas. However, the Río Chepo and the Río Chagres are sources of hydroelectric power.

The Río Chagres is one of the longest and most vital of the approximately 150 rivers that flow into the Caribbean. Part of this river was dammed to create Gatun Lake, which forms a major part of the transit route between the locks near each end of the canal. Both Gatun Lake and Madden Lake (also filled with water from the Río Chagres) provide hydroelectricity for the area of the former Canal Zone.

The Río Chepo, another major source of hydroelectric power, is one of the more than 300 rivers emptying into the Pacific. These Pacific-oriented rivers are longer and slower running than those of the Caribbean side. Their basins are also more extensive. One of the longest is the Río Tuira, which flows into the Golfo de San Miguel and is the nation's only river navigable by larger vessels.

Panama has a tropical climate. Temperatures are uniformly high- -as is the relative humidity--and there is little seasonal variation. Diurnal ranges are low on a typical dry-season day in the capital city, the early morning minimum may be 24° C and the afternoon maximum 29° C. The temperature seldom exceeds 32° C for more than a short time.

Temperatures on the Pacific side of the isthmus are somewhat lower than on the Caribbean, and breezes tend to rise after dusk in most parts of the country. Temperatures are markedly cooler in the higher parts of the mountain ranges, and frosts occur in the Cordillera de Talamanca in western Panama.

Climatic regions are determined less on the basis of temperature than on rainfall, which varies regionally from less than 1.3 to more than 3 meters per year. Almost all of the rain falls during the rainy season, which is usually from April to December, but varies in length from seven to nine months. The cycle of rainfall is determined primarily by two factors: moisture from the Caribbean, which is transported by north and northeast winds prevailing during most of the year, and the continental divide, which acts as a rainshield for the Pacific lowlands. A third influence that is present during the late autumn is the southwest wind off the Pacific. This wind brings some precipitation to the Pacific lowlands, modified by the highlands of the Península de Azuero, which form a partial rainshield for much of central Panama. In general, r 765ainfall l is much heavier on the Caribbean than on the Pacific side of the continental divide. The annual average in Panama City is little more than half of that in Colón. Although rainy-season thunderstorms are common, the country is outside the hurricane track.

Panama's tropical environment supports an abundance of plants. Forests dominate, interrupted in places by grasslands, scrub, and crops. Although nearly 40 percent of Panama is still wooded, deforestation is a continuing threat to the rain-drenched woodlands. Tree cover has been reduced by more than 50 percent since the 1940s. Subsistence farming, widely practiced from the northeastern jungles to the southwestern grasslands, consists largely of corn, bean, and tuber plots. Mangrove swamps occur along parts of both coasts, with banana plantations occupying deltas near Costa Rica. In many places, a multi-canopied rain forest abuts the swamp on one side of the country and extends to the lower reaches of slopes in the other.

Data as of December 1987