Abstract

Lake Zirahuen. a small (10.48 km²) tropical high-mountain lake located in the Mexican Novocain Axis, is under severe anthropogenic pressure. Its maximum depth is 43 m. The annual water balance is controlled by differences between rainfall, plus seepage, watershed runoff, and the main stream 'La Palma' plus evaporation. Tropical latitudinal conditions and high altitude produce thermal characteristics intermediate between temperate and tropical lakes. Transparency is good (up to 7.0 in). The nutrient relationship for N:P suggests that phosphorus remains limiting to primary productivity. Maximum phytoplankton chlorophyll a occurs in September at the end of the rainy season. Trophic state models suggest that Lake Zirahuen is an oligotrophic system. However, increasing erosion loads and untreated sewage input indicate the need for compatible watershed and lake management strategies which will ensure the conservation of the system and its sustainable development. © 1999 Elsevier Science Ltd and AEHMS. All rights reserved.

Keywords: Tropical lakes; High-altitude lakes; Lake Zirahuen; Trophic state; Water quality;                 Oligotrophic