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In this study, precipitation in Tropical South America in the 1931–2016 period is investigated by means of Principal Component Analysis and composite analysis of circulation fields. The associated dynamics are analyzed using the 20th century ERA-20C reanalysis. It is found that the main climatic processes related to precipitation anomalies in Tropical South America are: (1) the intensity and position of the South Atlantic Convergence Zone (SACZ); (2) El Niño Southern Oscillation (ENSO); (3) the meridional position of the Intertropical Convergence Zone (ITCZ), which is found to be related to Atlantic Sea Surface Temperature (SST) anomalies; and (4) anomalies in the strength of the South American Monsoon System, especially the South American Low-Level Jet (SALLJ). Interestingly, all of the analyzed anomalies are related to processes that operate from the Atlantic Ocean, except for ENSO. Results from the present study are in agreement with the state of the art literature about precipitation anomalies in the region. However, the added strength of the longer dataset and the larger study area improves the knowledge and gives new insights into how climate variability and the resulting dynamics are related to precipitation in Tropical South America.

In remote areas with steep topography, such as the Tropical Andes, reliable precipitation data with a high temporal resolution are scarce. Therefore, studies focusing on the diurnal properties of precipitation are hampered. In this paper, we investigated two years of data from Micro-Rain Radars (MRR) in Cuenca, Ecuador, and Huaraz, Peru, from February 2017 to January 2019. This data allowed for a detailed study on the temporal precipitation characteristics, such as event occurrences and durations at these two locations. Our results showed that the majority of precipitation events had durations of less than 3 h. In Huaraz, precipitation has a distinct annual and diurnal cycle where precipitation in the rainy season occurred predominantly in the afternoon. These annual and diurnal cycles were less pronounced at the site in Cuenca, especially due to increased nocturnal precipitation events compared to Huaraz. Furthermore, we used a fuzzy logic classification of fall velocities and rainfall intensities to distinguish different precipitation types. This classification showed that nightly precipitation at both locations was predominantly stratiform, whereas (thermally induced) convection occurred almost exclusively during the daytime hours.

In response to increasing pressures on water resources, watershed services management programs are implemented throughout the tropics. These programs aim to promote land management activities that enhance the quantity and quality of water available to local communities. The success of these programs hinges on our ability to (a) understand the impacts of watershed interventions on ecohydrology; (b) model these impacts and design efficient management programs; and (c) develop strategies to overcome barriers to practical policy development, including resource limitations or the absence of baseline data. In this paper, we review opportunities in ecohydrological science that will help address these three challenges. The opportunities are grouped into measurement techniques, modelling approaches, and access to resources in our hyperconnected world. We then assess management implications of both the knowledge gaps and the new research developments related to the effect of land management. Overall, we stress the importance of policy-relevant knowledge for implementing efficient and equitable watershed services programs in the tropics.

Precipitation forecast is fundamental for improving the management of water resources, for development projects and risk reduction. Due to its high variability, high quality rain forecasts are still a challenge. In the present study, a weather generator (WG) was used to study the quality of the forecast of daily rainfall occurrence. The WG was implemented using three variables as predictors: the binary variable precipitation occurrence of the previous day (Kt-1), the maximum and minimum temperatures of the previous day (Txt-1, Tnt-1, respectively); and two co-variables: monthly values of the observed Sea Surface Temperature Anomalies of the Regions 1+2 and 3.4 of El Niño-Southern Oscillation (Niño 1+2 and Niño 3.4 respectively). We found that the variables Kt-1, Tnt-1 and co-variable Niño 3.4 are those that improve the performance of the precipitation occurrence forecasting. There was a noticeable difference in the number of consecutive wet and dry spell days in the altitudinal gradient in a rainy period. We propose several hypotheses based on the use of WG, which allow the understanding of the functioning of the climate system and the improvement of the forecast of precipitation occurrence in a mountainous area., El pronóstico de precipitación es fundamental para mejorar la gestión de los recursos hídricos tanto para proyectos de aprovechamiento como de reducción de riesgos. Debido a su alta variabilidad, es un reto realizar un buen pronóstico de lluvia. En el presente estudio se empleó un generador climático (GC) para investigar la calidad del pronóstico de ocurrencia de precipitación diaria en una zona de montaña. El GC implementado usó como predictores a tres variables: la variable binaria ocurrencia del día anterior (Kt-1), las temperaturas máximas y mínimas del día anterior (Txt-1, Tnt-1, respectivamente); y dos covariables: las anomalías de la Temperatura mensual Superficial del Mar de las Regiones 1+2 y 3.4 de El Niño-Oscilación del Sur (Niño 1+2 y Niño 3.4 respectivamente). Determinamos que las variables Kt-1, Tnt-1 y la covariable Niño 3,4 mejoran el ajuste en el pronóstico. Encontramos diferencias notables en el número de días consecutivos secos y lluviosos en el gradiente altitudinal en un periodo lluvioso. El estudio permitió el planteamiento de varias hipótesis a partir del uso del GC las cuales ayudan a la comprensión del funcionamiento del sistema climático y el mejoramiento del pronóstico de precipitación.

Este artículo contrapone la actitud de confrontación entre las comunidades locales impulsadas por grupos de presión, en algunos casos con el apoyo de los gobiernos locales y las empresas mineras que pueden transformar su relación siguiendo un modelo de comunicación y cooperación empresarial. Varias de las grandes empresas mineras han adoptado recientemente un modelo de negociación corporativa, en el cual se considera un amplio espacio para tomar en cuenta las aspiraciones sociales y económicas de las comunidades que habitan en sectores de influencia de los proyectos mineros. Acciones propuestas que contribuyen a una actitud de colaboración son la inversión de tiempo en la creación de un modelo de comunicación, la negociación de acuerdos de impacto y beneficio mutuo, la participación de miembros de la comunidad en la organización y explotación de los servicios y el suministro de bienes, la capacitación de los comuneros en conservación y técnicas de restauración y las tecnologías relacionadas, y dotar de infraestructura y equipamiento que permita que las comunidades desarrollen actividades económicas independientes que se puedan mantener después del cierre de la mina. La participación de la comunidad científica local, eventualmente en asociación con los ecologistas, en las actividades de monitoreo, mitigación, rehabilitación y restauración ayudará a este sector a desarrollar las capacidades, lo cual será beneficioso para dar soporte a los programas educativos y de investigación relacionados a la temática. La participación de los gobiernos nacionales está relacionada a mejorar el marco legal y al desarrollo de protocolos de monitoreo más eficientes que permitan verificar si la mina se desarrolla de manera ética, social y ambientalmente responsable. This article states that the confrontational attitude between local communities pushed by lobbying groups, eventually with the support of local governments, and mining companies can be turned into a corporate communication and cooperation model. Several of the large mining companies recently adopted a corporate business model in which ample room is given to the social and economic desires of the communities living nearby mining sites. Proposed actions that contribute to a collaborative attitude are the investment of time in the setting up of a communication model, the negotiation of impact and benefit agreements, involving community members in the organization and exploitation of services and the provision of goods, training of locals in conservation and restoration techniques and related technologies, and making available infrastructure and equipment as to enable locals developing economic activities which they independently can continue after mine closure. Involving the local scientific community, eventually in association with environmentalists, in activities of monitoring, mitigation, remediation and restoration helps this sector to develop capacity which will be beneficial in educational and research related programs. Governments’ participation will culminate in a better legal framework and the development of more efficient protocols for the verification if mining is conducted in an ethical, social and environmental sound manner. Cuenca volumen 6, número 2

272 pp. llambi@ula.ve alesoto@ula.ve

Hay una fuerte demanda por parte de los responsables políticos de las predicciones sobre los posibles impactos del cambio climático sobre los recursos hídricos. Modelos ambientales integradas, combinando modelos climáticos e hidrológicos, a menudo se utilizan para este fin. En este trabajo se analiza el impacto de las incertidumbres relacionadas con los MCG en los estudios de impacto hidrológicos en los Andes tropicales. Un modelo hidrológico conceptual se calibra en los datos de cuatro cuencas de mesoescala, montañoso en el sur de Ecuador. Las entradas del modelo son entonces perturbados con anomalías proyectadas por 20 MCG disponibles en el Centro de Distribución de Datos del IPCC. Los resultados muestran que, en promedio, no se espera que la descarga mensual promedio a cambiar dramáticamente. Sin embargo, las descargas simuladas impulsadas por datos diferentes obligando modelo climático global pueden diferir ampliamente, con la predicción varía a menudo superando descarga de corriente. There is a strong demand from policy makers for predictions about the potential impacts of climate change on water resources. Integrated environmental models, combining climatic and hydrologic models, are often used for this purpose. This paper examines the impact of uncertainties related to GCMs in hydrological impact studies in the tropical Andes. A conceptual hydrological model is calibrated on data from four mesoscale, mountainous catchments in south Ecuador. The model inputs are then perturbed with anomalies projected by 20 GCMs available from the IPCC Data Distribution Centre. The results show that on average, the average monthly discharge is not expected to change dramatically. However, the simulated discharges driven by different global climate model forcing data can diverge widely, with prediction ranges often surpassing current discharge. Cuenca volumen 36; número 7

Los altos pastizales de altura de los Andes tropicales, conocido como páramo, son un ecosistema muy frágil y único. A pesar de las crecientes actividades humanas, muchos de sus procesos geomorfológicos e hidrológicos son todavía muy poco conocidos. Por consiguiente, celebramos el papel de Harden [Harden, CP 2006. Los impactos humanos sobre los sistemas fluviales de cabecera en los Andes del norte y centro. Geomorfología 79, 249-263.] Sobre "Los impactos humanos sobre los sistemas fluviales de cabecera en los Andes del norte y centro" como una valiosa contribución a una mejor comprensión de este complejo ecosistema. Sin embargo, en vista de la literatura disponible, nos gustaría complementar la interpretación de los resultados presentados y discutir algunas de las afirmaciones hechas en el papel. The high altitude grasslands of the tropical Andes, known as páramo, are a very fragile and unique ecosystem. Despite increasing human activities, many of its geomorphological and hydrological processes are still very poorly understood. We therefore welcome the paper of Harden [Harden, C.P., 2006. Human impacts on headwater fluvial systems in the northern and central Andes. Geomorphology 79, 249-263.] about "Human impacts on headwater fluvial systems in the northern and central Andes" as a valuable contribution to a better understanding of this complex ecosystem. However, in view of the available literature, we would like to complement the interpretation of the presented results and discuss some of the claims made in the paper. volumen 96; números 1-2