Water quality information is essential supporting decision making in water management processes. The lack of information restricts, at some point, the implementation of adequate sanitation, which is still scarce in developing countries. In this study, an ecosystemic water quality assessment was conducted in the Virilla river in Costa Rica, in a section of particular interest for future sanitation development. It included the monitoring of physical, chemical, microbiological and benthic macroinvertebrate parameters from 2014 to 2016. Mutivariate statistics and water quality indexes were used for data interpretation. Results indicated that water quality decreased downstream towards more urbanised areas. Particularly, extreme values of phosphorous, nitrogen and E. coli were found. Sample sites were grouped in two clusters, which were consistent with land use. Benthic macroinverterbrates diversity was predominantly represented by Baetidae, Chironomidae, Leptohyphidae, Hydropsychidae, Simuliidae and Physidae. They were mostly influenced by water temperature, nitrite, ammonium, soluble reactive phosphorous, total solids, alkalinity, nitrate and total suspended solids. Three water quality indexes consistently showed the poor condition of the water body. The overall results indicate that the main sources of pollution in the river are likely to be wastewater discharges. Thus, special efforts should be undertaken regarding its regulation in the country.

Tropical regions cover approximately 36% of the Earth's landmass. These regions are home to 40% of the world's population, which is projected to increase to over 50% by 2030 under a remarkable climate variability scenario often exacerbated by El Niño Southern Oscillation (ENSO) and other climate teleconnections. In the tropics, ecohydrological conditions are typically under the influence of complex land-oceanatmosphere interactions that produce a dynamic cycling of mass and energy reflected in a clear partition of water fluxes. Here, we present a review of 7 years of a concerted and continuous water stable isotope monitoring across Costa Rica, including key insights learned, main methodological advances and limitations (both in experimental designs and data analysis), potential data gaps, and future research opportunities with a humid tropical perspective. The uniqueness of the geographic location of Costa Rica within the mountainous Central America Isthmus, receiving moisture inputs from the Caribbean Sea (windward) and the Pacific Ocean (complex leeward topography), and experiencing strong ENSO events, poses a clear advantage for the use of isotopic variations to underpin key drivers in ecohydrological responses. In a sequential approach, isotopic variations are analyzed from moisture transport, rainfall generation, and groundwater/surface connectivity to Bayesian and rainfall-runoff modeling. The overarching goal of this review is to provide a robust humid tropical example with a progressive escalation from common water isotope observations to more complex modeling outputs and applications to enhance water resource management in the tropics.

Although the biodiversity of Costa Rican national parks, forests, and wetlands has been extensively surveyed, there has not been a watershed assessment that reflects their baseline water quality. Undoubtedly, the influx of 3.1 million visitors annually can lead to deterioration. Additionally, the country's movement toward 100% carbon neutral energy means reliance on capturing water for the production of hydroelectricity. The missing hydrologic data set is of immediate concern, as watershed health predicts total ecosystem health. This field-based project measures eight parameters (pH, temperature, fecal coliform, dissolved oxygen, biochemical oxygen demand, nitrates, total phosphates, turbidity) needed to assign a watershed quality index (WQI) value at nine national parks or protected areas. Overall, the WQI for the systems surveyed reflect good water quality. Results compared with US Environmental Protection Agency (EPA) and World Health Organization (WHO) drinking water standards indicate limited levels of contamination at most sites, with elevated signatures of nitrates, phosphates, turbidity, and/or fecal coliforms at few. The parks selected include coastal lowlands and central highlands; they also experience diverse tourist activities, degrees of use, and forest type that are challenges when managing land sustainably.

Introducción: La calidad del agua en una cuenca hidrográfica, y su uso potencial, se ven afectados por factores antrópicos y naturales. El río Tárcoles es el receptor final de aguas de la región central de Costa Rica, donde el tratamiento de aguas residuales es inadecuado o inexistente. Objetivo: Evaluar la contaminación del agua en el río y evaluar a los macroinvertebrados como bioindicadores del ecosistema. Métodos: Se realizaron evaluaciones fisicoquímicas, microbiológicas y de macroinvertebrados del agua superficial en cuatro sitios durante doce meses consecutivos, incluidos dos índices de calidad del agua (ICA-NSF y holandés). Hicimos visitas mensuales para la colocación y recolección de sustratos artificiales para macroinvertebrados acuáticos, y visitas bimensuales para la recolección de muestras de agua para análisis ex situ de los parámetros fisicoquímicos y microbiológicos. Además, se caracterizó el uso del suelo en la parte baja de Tárcoles a partir de archivos tipo “raster” de cobertura. Resultados: Algunas variables fisicoquímicas tuvieron concentraciones similares a las informadas para otros ríos costarricenses, mientras que el oxígeno fue inferior. Las variables microbiológicas indicaron altos niveles de contaminación, especialmente en la época de lluvias. En la estación seca, hubo más macroinvertebrados acuáticos, siendo Chironomidae, Oligochaeta e Hydrobiidae los más abundantes. La contaminación de los ríos se clasifica como "incipiente" según el índice holandés y como "calidad media" según el ICA-NSF. Conclusiones: la contaminación del río Tárcoles se debe principalmente a un uso inadecuado del suelo y actividades antrópicas. Recomendamos un plan de gestión de cuencas e investigación sobre la salud del ecosistema y la conservación de especies vulnerables.

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