Problems related to water resource use
Lake Nicaragua is one of the largest reservoirs of fresh water in the Americas. Its outflow through the San Juan River (averaging 475 m³/sec), as well as its capacity for storage, high water quality, its geographic location, and its connection with the Caribbean Sea through the San Juan River are features that render it attractive for a number of purposes, such as navigation, energy production, irrigation, potable water supply, tourism, recreation, and fishing, to name the principal ones. For many years, transportation on the San Juan River and Lake Nicaragua has been an important factor in the socioeconomic and political development of Nicaragua. Interest in the construction of an inter-oceanic route tapping the potential of the San Juan River and Lake Nicaragua dates back to Spanish colonial times. The first historical data records that the San Juan River and Lake Nicaragua were used to transport the riches discovered on the western coasts of South America and shipped to Spain during the conquest of the continent. History shows that since 1504, Nicaragua has made over 10 attempts to construct an inter-oceanic canal. To date, however, none of the projects has come to fruition.
With the discovery of gold in California (1848), transiting North Americans sought a faster route to the gold mines through the San Juan River and Lake Nicaragua. Reports from that time indicate that in 1853 some 20,800 traveled from the East Coast to the West Coast of the United States using that route. Other data show that at that time some 2,000 passengers were transported via that route on a monthly basis. However, an earthquake that occurred in July 1863 increased sedimentation in the San Juan River mouth, greatly increasing the difficulties of navigating that part of the river. Later, the construction of the transcontinental railway across the US in 1869 put an end to the great demand for passenger transport through Nicaragua.
Nevertheless, at the beginning of this century, interest in commercial navigation through Lake Nicaragua resumed. Of the studies conducted since the 1900s on the construction of an inter-oceanic canal, the following are noteworthy:
Further projects related to the construction of an inter-oceanic canal have been presented more recently, using either the waters of the San Juan River and Lake Nicaragua or building a railway connecting the Caribbean Sea to the Pacific Ocean, or a combination of the two.
A number of boats operated on Lake Nicaragua and in the San Juan River and its tributaries, facilitate the trading of goods with the Pacific region of the country and the transport of passengers to towns located in the western sector of the lake and in the Pacific zone. In some communities like North San Juan, existing water-based transportation routes between communities in Costa Rica is well known. Practically all the trade in between these communities takes place through Puerto Viejo in the Sarapiquí canton. Also, emergency medical attention and sometimes other basic services, such as telephone communications with Nicaragua and education, are obtained through Costa Rica, along the waterways.
The main port facilities located in the SJRB are the following: San Juan del Norte, El Castillo, and Sábalos, located on the San Juan River; Granada, San Jorge, San Carlos, and San Miguelito, located on the banks of Lake Nicaragua; and Moyogalpa, Altagracia, and Solentiname, located on Ometepe Island and in the Solentiname Archipelago, respectively. Los Chiles, Puerto Viejo, and Barra Colorado are ports situated on the tributaries flowing from the southern sector of the basin. A feasibility study of the local transportation system in Lake Nicaragua and in the San Juan River conducted in 1970 found that the economic and financial benefit of the project was positive. Since then, however, there have been no new estimates on local navigation in these water bodies.
Navigation on the San Juan River and in Lake Nicaragua are affected by the progressive sedimentation of both water bodies. Navigation is also an important source of pollution of the water resources, due to the fact that boats are washed and serviced in both water bodies.
The waterbodies, therefore, become depositaries of hydrocarbon residue, agricultural chemicals, basic grains, pigs, domesticated animals, and other products that are transported across these bodies of water.
The basin’s water resources have great potential for hydroelectric generation. The considerable flow rates, combined with significant altitude changes within the basin, have led to the development of this type of project in the SJRB. To date, there are four known hydroelectric development proposals to use the average flow rate at which Lake Nicaragua empties into the San Juan River as the source of the power supply. None of these options have been discarded as yet. The projects are: Tipitapa-Tamarindo, Brito, Brito Residual, and Interlagos.
The construction of any of these projects will mean substantive changes in the average flow rate of the San Juan River, reducing it by some 36%. This will undoubtedly have a strong impact on navigation in the river. Aspects to be considered if these projects are implemented should be their effects on the aquatic life in the San Juan River and Lake Nicaragua, the flora and fauna existing in the area to be inundated by the proposed dams, and the environmental impact that will result from all the associated construction works.
In addition to the large projects discussed above, there are currently several public and private hydroelectric projects in the southern sector of the SJRB, which are at different stages of development. The private projects are approved by the ICE and carried out by private firms.
The possible conflicts in water use are one of the aspects evoked whenever an option for hydroelectric power or inter-oceanic canal construction is presented, especially since between 300 and 400 m³/sec of the existing river flows abstracted to meet the requirements for potable water and irrigation water supplying suitable farmland in the Pacific Region of Nicaragua.
On the banks of lakes Managua and Nicaragua and in the León-Chinandega plain, there are 742,000 hectares of land suitable for irrigation (152,000 ha in the Lake Managua zone, 432,000 ha in the area of Lake Nicaragua, and 158,000 distributed in the León-Chinandega area). The potential, available water in the León-Chinandega plain and along the banks of the lakes is approximately 745 MMC. This volume could provide the water supply to irrigate approximately 138,000 ha, resulting in a shortfall in the amount needed to irrigate some 600,000 ha. To make up for this shortfall, a number of different alternative projects have been proposed, all of them drawing on Lake Nicaragua as the source. The most recent study, "Irrigation Strategy for Pacific Nicaragua", envisaged damming the waters of the San Juan River at San Isidro, maintaining the water level of Lake Managua at 32 masl, draining water from Lake Nicaragua into Lake Managua by constructing a canal on the Tipitapa River, and pumping the water available up to the 100 masl mark. This scheme would then irrigate, using gravity, the 600,000 ha needing irrigation that are below this elevation. This project envisages generating power through the Tamarindo River, the replenishing of Lake Managua and the provision of drinking water supplies to towns requiring this service, including Managua.
Like the hydroelectric projects, this project will change the average flow rate of the San Juan River, which, in turn, will impact heavily on navigation of the river. Aspects to be considered with this project should be the effects on aquatic life related to the San Juan River, lakes Nicaragua and Managua, the existing flora and fauna in the area to be flooded by the proposed dam, and the environmental impact of the construction and all related works. There is conflict in the use of water for this irrigation project because, the wider the area irrigated, the less water available for power generation and the drinking water supply.
Though the drinking water supply is a problem in the basin, it does not place any particular pressure on the resource because of the size of the demand. However, municipal and industrial wastewater does indeed pose a threat to water quality. Due to the fact that most of the population deposits its used water in riverbeds, streams, or directly in the lake or river with no prior treatment, the quality of the water of those bodies of water has noticeably deteriorated. Critical points are San Miguelito, San Jorge, Granada, Juigalpa, San Carlos, El Castillo, Sábalos and San Juan del Norte.
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