Paraguay is a landlocked country in South America, in the center of the continent, just south of the equator. Nevertheless, it has harbours on the Paraguay and Paraná rivers, which are connected to the Atlantic Ocean, through the Paraná-Paraguay Waterway. The inhabitants are mostly native Guaraní people, more than 90% of the population speaks various dialects of the Guaraní language. Spanish and Guaraní are both official languages.
The Río Paraguay divides the country into two different regions. The Región Oriental (eastern region) is humid and mostly tropical. While the amount of rainfall increases from Río Paraguay from savannah over monsoon to rainforest, the easternmost part of the country is located further to the south and thus temperate with hot summers but no dry season. Obviously this part is the most populated part with the big cities, but also the most fertile part.
The Región Occidental (western region) is officially called Western Paraguay and also known as the Chaco. The Gran Chaco, Chaco Plain or Dry Chaco is a sparsely populated, hot and semiarid lowland which extends over eastern Bolivia, western Paraguay, northern Argentina, and western Brazil. It is the rain shadow of the Andes, which results in very low precipitation, on the other hand there are massive rivers which cross the area from the Andes to the Amazonas. The area is mostly an alluvial sedimentary plain and due to the lack of rain and the loose sediments there are very few caves.
Named after the native Guaraní people, the Guarani Aquifer is the second largest known aquifer system in the world. It covers 1.2 Million km² beneath Argentina, Brazil, Paraguay, and Uruguay. The rocks consist primarily of fluvial sandstones of the Piramboia Formation and aeolian sandstones of the Botucatu Formation. Those rocks have a big porosity, and so they can contain a high amount of groundwater and even allow a slow flow of water. Additionally, they are overlain by early Cretaceous basalts of the Serra Geral Formation, which have a low permeability keeping the water underground, a so-called aquitard. While aquifers are often karst areas, this one is not, which makes it less vulnerable to contamination. On the other side there are no caves and karst features we can list.
The most important karst area is probably the area of Vallemí or Valle-Mi in the district of San Lázaro, Concepción. It has a karstified outcrop of limestone with 66 km² large and has 54 known caves. As it is one of the rare limestone areas it is also threatened by the cement industry, the town is the home of the quarry and cement factory of the Industria Nacional de Cemento (INC).