Evaluación de los productos Tropical Rainfall Measuring Mission (TRMM) y Global Precipitation Measurement (GPM) en el modelamiento hidrológico de la cuenca del río Huancané, Perú

El objetivo de esta investigación fue evaluar los productos grillados de precipitación de la Tropical Rainfall Measuring Mission (TRMM) y de la Global Precipitation Measurement (GPM), en el modelamiento hidrológico en la cuenca del río Huancané, del Altiplano peruano. Al comparar la precipitación media diaria de los productos 3B42RT, 3B42V7 e IMERG respecto a la lluvia media diaria de la cuenca (abril 2014 – diciembre 2015), IMERG representa mejor los patrones de precipitación (R2: 0,38) pero no cuantifica adecuadamente la intensidad (BIAS: -32%). El producto 3B42V7 capta muy bien la intensidad de lluvia en contraste con el 3B42RT que presenta elevadas sobrestimaciones. Una evaluación de estos productos sin corregir en el modelo hidrológico GR4J, evidencia que, el producto 3B42V7 es la mejor opción para la estimación de las descargas en periodos de avenida. Sin embargo, al realizar la corrección del sesgo al promedio de IMERG, las estimaciones de lluvia mejoran (R2: 0,9; BIAS: -10,1%), en consecuencia, IMERG corregido sería el mejor producto de precipitación. Estos resultados preliminares están limitados al análisis de un corto periodo, sin embargo, a medida que se liberan más datos del IMERG, serán necesarios más estudios que exploren su utilidad en aspectos de hidrología y cambio climático

Rainfall thresholds estimation for shallow landslides in Peru from gridded daily data

This work aims to generate and evaluate regional rainfall thresholds obtained from a combination of high-resolution gridded rainfall data, developed by the National Service of Meteorology and Hydrology of Peru, and information from observed shallow landslide events. The landslide data were associated with rainfall data, determining triggering and non-triggering rainfall events with rainfall properties from which rainfall thresholds are determined. The validation of the performance of the thresholds is carried out with events that occurred during 2020 and focuses on evaluating the operability of these thresholds in landslide warning systems in Peru. The thresholds are determined for 11 rainfall regions. The method of determining the thresholds is based on an empirical–statistical approach, and the predictive performance of the thresholds is evaluated with true skill statistics. The best predictive performance is the mean daily intensity–duration (Imean−D) threshold curve, followed by accumulated rainfall E. This work is the first estimation of regional thresholds on a country scale to better understand landslides in Peru, and the results obtained reveal the potential of using thresholds in the monitoring and forecasting of shallow landslides caused by intense rainfall and in supporting the actions of disaster risk management

Hydrological Modeling of the Peruvian-Ecuadorian Amazon Basin Using GPM-IMERG Satellite-Based Precipitation Dataset

In the last two decades, rainfall estimates provided by the Tropical Rainfall Measurement Mission (TRMM) have proven applicable in hydrological studies. The Global Precipitation Measurement (GPM) mission, which provides the new generation of rainfall estimates, is now considered a global successor to TRMM. The usefulness of GPM data in hydrological applications, however, has not yet been evaluated over the Andean and Amazonian regions. This study uses GPM data provided by the Integrated Multi-satellite Retrievals (IMERG) (productfinal run) as input to a distributed hydrological model for the Amazon Basin of Peru and Ecuador for a 16-month period (from March 2014 to June 2015) when all datasets are available. TRMM products (TMPA V7, TMPA RT datasets) and a gridded precipitation dataset processed from observed rainfall are used for comparison. The results indicate that precipitation data derived from GPM-IMERG correspond more closely to TMPA V7 than TMPA RT datasets, but both GPM-IMERG and TMPA V7 precipitation data tend to overestimate, compared to observed rainfall (by 11.1 and 15.7 , respectively). In general, GPM-IMERG, TMPA V7 and TMPA RT correlate with observed rainfall, with a similar number of rain events correctly detected (20). Statistical analysis of modeled streamflows indicates that GPM-IMERG is as useful as TMPA V7 or TMPA RT datasets in southern regions (Ucayali basin). GPM-IMERG, TMPA V7 and TMPA RT do not properly simulate streamflows in northern regions (Maran and Napo basins), probably because of the lack of adequate rainfall estimates in northern Peru and the Ecuadorian Amazon

Determinación de Vulnerabilidad a la Sequía en el Perú

La sequía es uno de los peligros con más impactos negativos y costosos en términos económicos. Asimismo, el impacto de la sequía varía espacialmente en las regiones, sobre todo donde los elementos expuestos vulnerables podrían aumentar el grado de riesgo de la sequía en determinadas zonas. El presente estudio tuvo por objetivo determinar áreas vulnerables a la sequía en el Perú desde un enfoque multidimensional, utilizando indicadores sociales, económicos y ambientales. La metodología consistió en nueve pasos: desde identificación de la zona de estudio, selección de indicadores disponibles, y procesamiento de la información (Paso 1, 2 y 3), posteriormente se realiza el análisis de pesos, normalización de indicadores y ajuste a la función de distribución de probabilidad “Beta” (pasos 4, 5, 6 y 7), finalmente se realiza la clasificación de grado de vulnerabilidad y mapeo (paso 8 y 9). Los resultados mostraron que, los departamentos de La Libertad y Tacna presentaron los mayores porcentajes de distritos con "Alta" y “Muy alta” vulnerabilidad a la sequía, registrando un 27.54 % y 31.25 %, respectivamente. En la región sierra, los departamentos de Huancavelica y Puno registraron mayor porcentaje de distritos con vulnerabilidad “Alta” y “Muy alta” con 33.86 % y 35.71% respectivamente. Igualmente, en la selva peruana, Amazonas y San Martín se identifica un preocupante 27.38 % y 27.27 %, de distritos clasificados como "Alta" vulnerabilidad

Regionalización de la precipitación, su agresividad y concentración en la cuenca del río Guayas, Ecuador

A agressividade das chuvas contribui com a erosão do solo nas regiões de alta montanha e, portanto, para a sedimentação na parte inferior da bacia. A redução da incerteza sobre a agressividade das chuvas nas regiões costeiras e andinas contribui para a formulação de medidas de mitigação que contribuem para a redução da erosão e perda de nutrientes. Este estudo apresenta uma análise espacial e temporal da agressividade climática na bacia do rio Guayas, localizada na região da costa e Andes do Equador. Foram selecionados dados mensais registrados de 30 estações pluviométricas para o período 1968-2014. As zonas de precipitação homogênea foram determinadas usando o método de k-médias. Os resultados indicaram duas regiões homogêneas predominantes, a primeira localizada a oeste da zona costeira e andina (85,2% da área da bacia), com um índice de agressividade alto e muito alto, enquanto a distribuição da precipitação na segunda região (Alta montanha) foi de muito baixa a baixa agressividade. O maior potencial de agressividade da chuva corresponde a um maior acúmulo de precipitação médio anual, o que indica uma alta influência sazonal das chuvas, ou seja, uma quantidade maior de chuva pode precipitar em um número reduzido de meses consecutivos. Os valores de concentração revelam um gradiente regional na direção leste-oeste que tem variação sazonal de moderada a forte. As análises das tendências da concentração mensal das chuvas não mostram mudanças significativas no período do estudo. Porém, nossas descobertas explicam o motivo das regiões oeste e sul da bacia do rio Guayas estarem expostas a problemas de sedimentação na parte inferior, resultado da capacidade erosiva da chuva na parte superior e média da bacia.The aggressiveness of the rain contributes to the erosivity of the soil in high mountain regions, and therefore to the sedimentation in the lower part of the watershed. The reduction of uncertainty about the aggressiveness of rain in coastal and Andean regions contributes to the formulation of mitigation measures that contribute to the reduction of erosion and loss of nutrients. This study presents a spatial and temporal analysis of climatic aggressiveness in the Guayas river watershed located on the coast and the equatorial Andes. Registered monthly data of 30 rainfall stations for the period of 1968-2014 was selected. Homogeneous precipitation zones were determined by the k-means method. The results indicated two predominant homogenous regions, the first located to the west in the coastal and Andean zone (85.2% of the area of the Watershed), with a high and very high aggressiveness index, while the distribution of precipitation in the second region (High mountain) resulted from very low to low aggressiveness. The greater potential aggressiveness of rain corresponds to a greater accumulation of average annual rainfall, which indicates a high seasonal influence of rainfall, that is, a greater amount of rainfall can precipitate in a reduced number of consecutive months. The concentration values reveal a regional gradient in the east-west direction, which goes from moderately to strongly seasonal. The trend analysis of the monthly rainfall concentration shows no significant changes in the study period. However, our findings explain why the western and southern region of the Guayas river watershed is exposed to sedimentation problems in the lower part, product of the erosive capacity of rain in the higher and middle part of the watershed.La agresividad de la lluvia contribuye a la erosividad del suelo en regiones de alta montaña, y por tal a la sedimentación en la parte baja de la cuenca. La reducción de incertidumbre acerca de la agresividad de la lluvia en regiones costeras y andinas contribuye a la formulación de medidas de mitigación que contribuyan a la reducción de erosión y pérdida de nutrientes. Este estudio presenta un análisis espacial y temporal de la agresividad climática en la cuenca del río Guayas ubicada en la costa y Andes ecuatoriales. Se seleccionó datos mensuales registrados de 30 estaciones pluviométricas para el periodo de 1968-2014. Se determinó zonas homogéneas de precipitación mediante el método k-means. Los resultados indicaron dos regiones homogeneas predominantes, la primera ubicada al oeste en la zona costera y andina (85.2% del área de la Cuenca), con un índice de agresividad alto y muy alto, mientras que la distribución de la precipitación en la segunda región (Alta montaña) resultó de muy baja a baja agresividad. La mayor agresividad potencial de la lluvia le corresponde una mayor acumulación de precipitación promedio anual, lo que indica una alta influencia estacional de las lluvias, i.e, una mayor cantidad de lluvia puede precipitar en un número reducido de meses consecutivos.  Los valores de concentración revelan una gradiente regional en dirección este-oeste, que va de moderadamente a fuertemente estacional. El análisis de tendencias de la concentración de lluvia mensual no muestra cambios significativos en el periodo de estudio. No obstante, nuestros hallazgos explican el porqué la región oeste y sur de la cuenca del río Guayas está expuesta a problemas de sedimentación en la parte baja, producto de la capacidad erosiva de la lluvia en la parte alta y media de la cuenca

Impact of the global warming hiatus on Andean temperature

Abstract The recent hiatus in global warming is likely to be reflected in Andean temperature, given its close dependence on tropical Pacific sea surface temperature (SST). While recent work in the subtropical Andes has indeed documented a cooling along coastal areas, trends in the tropical Andes show continued warming. Here we analyze spatiotemporal temperature variability along the western side of the Andes with a dense station network updated to 2010 and investigate its linkages to tropical Pacific modes of variability. Results indicate that the warming in tropical latitudes has come to a halt and that the subtropical regions continue to experience cooling. Trends, however, are highly dependent on elevation. While coastal regions experience cooling, higher elevations continue to warm. The coastal cooling is consistent with the observed Pacific Decadal Oscillation (PDO) fingerprint and can be accurately simulated using a simple PDO-analog model. Much of the PDO imprint is modulated and transmitted through adjustments in coastal SST off western South America. At inland and higher-elevation locations, however, temperature trends start to diverge from this PDO-analog model in the late 1980s and have by now emerged above the 1σ model spread. Future warming at higher elevation is likely and will contribute to further vertical stratification of atmospheric temperature trends. In coastal locations, future warming or cooling will depend on the potential future intensification of the South Pacific anticyclone but also on continued temperature dependence on the state of the PDO

Hydrological Response Assessment of Land Cover Change in a Peruvian Amazonian Basin Impacted by Deforestation Using the SWAT Model

The watershed hydrologic conditions in the Madre de Dios (MDD) Basin in the Peruvian Amazon have been irreversibly impacted by deforestation and changes in land cover. These changes have also had detrimental effects on the geomorphology, water quality, and aquatic habitat within the basin. However, there is a scarcity of hydrological modeling studies in this area, primarily due to the limited availability of hydrometeorological data. The primary objective of this study was to examine how deforestation impacts the hydrological conditions in the MDD Basin. By implementing the Soil and Water Assessment Tool (SWAT) model, this study determined that replacing 12% of the evergreen broadleaf forest area with bare land resulted in a significant increase in surface runoff, by 38% monthly, a 1% annual reduction of evapotranspiration, and an average monthly streamflow increase of 12%. Changes in spatial patterns reveal that the primary impacted watershed is the Inambari River subbasin, a significant tributary of the Madre de Dios River. This area experiences an annual average surge of 187% in surface runoff generation while witnessing an annual average reduction of 8% in evapotranspiration. These findings have important implications, as they can contribute to instances of flooding and extreme inundation events, which have already occurred in the MDD region

Assessment of Present and Future Water Security under Anthropogenic and Climate Changes Using WEAP Model in the Vilcanota-Urubamba Catchment, Cusco, Perú

Water is an essential resource for social and economic development. The availability of this resource is constantly threatened by the rapid increase in its demand. This research assesses current (2010–2016), short- (2017–2040), middle- (2041–2070), and long-term (2071–2099) levels of water security considering socio-economic and climate change scenarios using the Water Evaluation and Planning System (WEAP) in Vilcanota-Urubamba (VUB) catchment. The streamflow data of the Pisac hydrometric station were used to calibrate (1987–2006) and validate (2007–2016) the WEAP Model applied to the VUB region. The Nash Sutcliffe efficiency values were 0.60 and 0.84 for calibration and validation, respectively. Different scenarios were generated for socio-economic factors (population growth and increased irrigation efficiency) and the impact of climate change to evaluate their effect on the current water supply system. The results reveal that water availability is much higher than the current demand in the VUB for the period (2010–2016). For short-, middle- and long term, two scenarios were considered, “Scenario 1” (RCP 4.5) and “Scenario 2” (RCP 8.5). Climate change scenarios show that water availability will increase. However, this increase will not cover the future demands in all the sub-basins because water availability is not evenly distributed in all of the VUB. In both scenarios, an unmet demand was detected from 2050. For the period 2071–2099, an unmet demand of 477 hm3/year for “Scenario 1” and 446 hm3/year for “Scenario 2” were estimated. Because population and agricultural demands are the highest, the effects of reducing the growth rate and improving the irrigation structure were simulated. Therefore, two more scenarios were generated “Scenario 3” (RCP 4.5 with management) and “Scenario 4” (RCP 8.5 with management). This socio-economic management proved to be effective in reducing the unmet demand up to 50% in all sub-basins for the period 2071–2099. © 2023 by the authors

Caracterización del peligro por movimiento de masa debido a lluvias extremas en la quebrada Malanche, distrito de Punta Hermosa

Se realizaron simulaciones para periodos de retorno de 5, 10, 25, 50, 100 y 500 años del fenómeno de flujos de escombros en la quebrada Malanche, usando los modelos numéricos HEC-HMS y HEC-RAS. Se analizó la frecuencia de la precipitación máxima en 24 horas de la estación Antioquia, estimando magnitudes para diversos periodos de retorno. Se recomienda estudiar la variabilidad espacial de las tormentas y aumentar la densidad de estaciones de lluvia en tiempo real. Se simuló el proceso precipitación-escorrentía con HEC-HMS, recomendándose un análisis de sensibilidad de la red de drenaje y la rugosidad superficial, además de simular la producción de sedimentos para distintos periodos de retorno como entrada al modelo HEC-RAS. No se validaron las simulaciones por falta de mediciones de flujo y sedimentos en la quebrada Malanche, pero los resultados son considerados razonables. Se recomienda instalar cámaras LSPIV para registrar flujos durante lluvias intensas y usar métodos geomorfológicos con drones para calibrar los procesos físicos. El área urbana cercana a la playa no se vería afectada para los periodos de retorno estudiados, aunque se requeriría un evento extremo superior al de 500 años para simular el fenómeno de 2023. Las medidas de mitigación tomadas en 2023, como la limpieza del cauce, serían efectivas. Pampacta y Santa Rosa de Punta Hermosa sí se verían afectadas, causando daños materiales y posibles impactos directos en la población. Se recomienda realizar campañas de concientización sobre el peligro de los movimientos de masa. Para definir umbrales de inundación en un sistema de alerta temprana, se sugiere considerar la intensidad media de la precipitación y la duración total de la tormenta, simulando diferentes escenarios basados en estos factores

A combined view on precipitation and temperature climatology and trends in the southern Andes of Peru

In the southern Peruvian Andes, communities are highly dependent on climatic conditions due to the mainly rain-fed agriculture and the importance of glaciers and snow melt as a freshwater resource. Longer-term trends and year-to-year variability of precipitation or temperature severely affect living conditions. This study evaluates seasonal precipitation and temperature climatologies and trends in the period 1965/66–2017/18 for the southern Peruvian Andes using quality-controlled and homogenized station data and new observational gridded data. In this region, precipitation exhibits a strong annual cycle with very dry winter months and most of the precipitation falling from spring to autumn. Spatially, a northeast–southwest gradient in austral spring is observed, related to an earlier start of the rainy season in the northeastern partof the study area. Seasonal variations of maximum temperature are weak withan annual maximum in austral spring, which is related to reduced cloud coverin austral spring compared to summer. On the contrary, minimum tempera-tures show larger seasonal variations, possibly enhanced through changes inlongwave incoming radiation following the precipitation cycle. Precipitationtrends since 1965 exhibit low spatial consistency except for austral summer,when in most of the study area increasing precipitation is observed, and in aus-tral spring, when stations in the central-western region of the study area regis-ter decreasing precipitation. All seasonal and annual trends in maximum temperature are larger than trends in minimum temperature. Maximum temperature exhibits strong trends in austral winter and spring, whereas minimum temperature trends are strongest in austral winter. We hypothesize, that these trends are related to precipitation changes, as decreasing (increasing) precipita-tion in spring (summer) may enhance maximum (minimum) temperature trends through changes in cloud cover. El Niño Southern Oscillation (ENSO), however, has modifying effects onto precipitation and temperature, and thereby leads to larger trends in maximum temperatures