The Neiba Valley, situated in the southwestern portion of the Republic between the Neiba and the Baboruco Mountains is more regular. It is part of the valley which stretches from Neiba Bay, in Santo Domingo, to Port-au-Prince in Haiti. The Dominican portion is 65 miles long by 12 miles wide, and over one-half of its area is covered by the waters of Lake Enriquillo. The peninsula south of the Baboruco Mountains is an uneven plateau.
In the very center of the Republic, surrounded on all sides by lofty mountains of the central group, is Constanza Valley, rich but to-day almost inaccessible. No less rich, but many times larger, is the other interior plain, known as the Eastern or Central Valley, a succession of fertile valleys, extending from the Neiba River to St. Raphael, almost 115 miles, with a width of from nine to twenty miles. The entire plain is claimed by the Dominican Republic, but more than half is in possession of Haiti.
All these various valleys and plains enjoy the advantage of being watered by a comprehensive network of rivers of greater or less size. Many of the streams are navigable for miles in the lower part of their course by boats and canoes, affording means of communication to which the wretched condition of the land highways gives added importance.
The largest river of the Republic is the Yaque del Norte, some 240 miles in length, which rises on the slope of Yaque Peak, describes a circuitous northerly course, receiving numerous mountain affluents, until it reaches the vicinity of the city of Santiago de los Caballeros, whence, turning northwesterly it flows through the Santiago Valley, being reinforced by scores of tributaries. Its waters are finally discharged partially into Monte Cristi Bay and partly through its many mouthed delta into Manzanillo Bay. Detritus and driftwood brought down by the river, for many years entirely filled the Monte Cristi channel, and still constitute barriers which cause large lagoons to form in the delta and to inundate extensive tracts of rich farmland. Though the bars at its entrance render the river inaccessible for larger boats, it is navigable for canoes over its entire course in the Santiago Valley.
Another large river is the yellow Yuna, which waters the eastern part of the Cibao Valley. Rising in the mountains near the center of the Republic, it directs its course to the Royal Plain where it receives the waters of the rapid Camu, and thence flows eastwardly and enters Samana Bay through a marshy delta, its total length being over 200 miles. Part of its waters find their way through the great swamp, the Gran Estero, into the Atlantic Ocean. Up to its junction with the Camu, a distance of some 30 miles, the Yuna is navigable by boats and barges, and above the junction both the Yuna and the Camu are navigable by canoes for nearly 30 miles more though there are shallow stretches where the streams run rapidly and great care is necessary. In former days, the Yuna was one of the chief outlets of the Cibao; freight and passengers were transported over its course to Samana Bay and on the waters of the Bay to the town of Samana where transshipment to larger vessels took place. With the establishment of the railroad from La Vega to Sanchez, the river has lost much of its old-time importance.
The third largest river is the Neiba or Yaque del Sur, which rises near the sources of the Yaque del Norte and pursues a southerly direction for some 180 miles, emptying into Neiba Bay. The repetition of geographical means is one of the peculiarities of Santo Domingo. Thus there are two rivers and a mountain named Yaque, several mountains named Cucurucho, a mountain-range and two cities named Macoris while in a host of minor instances rivers, mountains and districts in different parts of the country have identical names. The repetition of names seems all the more curious as the Dominicans have not hesitated to change historic names of towns and streets. The Yaque del Sur, or Neiba River, receives several copious affluents, the largest one being the San Juan River. Much of the lumber exported at Barahona is floated down the Yaque and the river is navigable about 20 miles for flat-bottomed boats, though rapids and rocky ledges interpose obstacles.
The other rivers of the southern part of Santo Domingo are much smaller. The principal one is the Ozama, at the mouth of which the capital city is located. This river is about 60 miles in length and carries a surprising amount of water. Being navigable by barges for 9 miles from its mouth and by canoes for 15 miles, it forms an important avenue of supply for Santo Domingo City. In the three miles from its junction with the Isabela to the sea, its depth is about 24 feet, but over the sandbar at its mouth but 15 feet. Two rivers in the southeastern peninsula, the Macoris and the Soco furnish valuable outlets for the products of the sugar estates on their banks. A number of Dominican streams offer peculiarities. In the mountains there are brooks which gush out of the hillside, merrily ripple on for miles and vanish into the ground as mysteriously as they came. A number of coast streams sink into the sand of the beach, just before reaching the ocean. The Brujuelas River, which rises on the edge of the great plains, northwest of Bayaguana, flows south 25 miles through the plains and disappears in the ground a mile from the sea. Most streams ordinarily insignificant and innocent looking, are in a surprisingly short space of time converted by rains into raging torrents. The most formidable of these torrential rivers is the Nizao which flows into the Caribbean Sea near Point Palenque. In the lower part of this river's course its bed is about a mile wide, of which only a small portion is covered by the several branches of the river, the remainder being taken up with sandbanks, gravel beds, marshy tracts and stagnant bayous; and so frequently and erratically does the river change its channels, and to such sudden rises is it subject, that the local authorities are obliged to keep guides stationed on its banks almost continuously, in order to direct travelers across.
The rapids and cascades of Dominican streams are pregnant with possibilities, but up to the present time they have remained in their pristine condition, nor is their energy utilized to drive a single piece of machinery. The largest and most beautiful waterfall of the island is doubtless that of the Jimenoa River, in the mountains some ten miles south of the city of La Vega, where the Jimenoa rushes over a precipice one hundred feet in height, producing clouds of spray and a roar that can sometimes be perceived as far as Jarabacoa, six miles away. Another beautiful fall is that of the Dajabon River, on the Haitian frontier, 30 feet in height, and there are notable cascades also on the Comate River, near Bayaguana, on the great plains; on the Nigua and Higuero Rivers, not many miles from Santo Domingo City; on the Inova River, near the town of San José de las Matas; and on the Guaranas River, on the Haitian frontier in the commune of Neiba.
The only lakes of any size are two which lie in the Neiba Valley, the larger one, Lake Enriquillo, being comprised entirely within Dominican territory, while of the smaller one, variously called Etang Saumatre, or Lake Azuei, or Laguna del Fondo, through which the frontier line passes, less than one-fourth is under Dominican jurisdiction. They are both very picturesque, and with the greenish color of their water and their arid mountain surroundings recall portions of Lake Titicaca in Bolivia. In stormy weather they become as rough as the ocean. Lake Enriquillo derives its name from the last Indian cacique of the Island, the romantic chieftain Enriquillo, who after fiercely resisting the Spaniards finally in 1533 concluded an honorable peace with them on the island of Cabras in the center of this lake. The lake is over 70 miles in circumference, having a length of about 33 miles and a width ranging from 3 to 9 miles, Cabras Island, 6 miles long by one in width, is the home of herds of goats. Lake Azuei is but 15 miles in length with a width of from 2 to 7 miles.
Though the two lakes are scarcely five miles apart, Lake Enriquillo is 102 feet below and Lake Azuei 56 feet above sea-level. Both lakes receive the waters of several small fresh water creeks, yet they apparently have no outlet and their water is salt, that of Lake Azuei only slightly, but that of Lake Enriquillo more so than the sea. On Cabras Island, however, there is a fresh water spring, and three lagoons to the east and south of Lake Enriquillo also contain fresh water. Lake Azuei often shows the paradox of going down during the rainy season and rising during the dry season; the phenomenon is attributed to the presence of springs at the bottom of the lake, which are unusually copious at the end of the rainy season. Both lakes have at least one variety of ocean fish, though the nearest point of the seacoast is some twenty miles distant; turtles abound in both and there are many alligators in Lake Enriquillo and a few in Lake Azuei.