Rainfall retention and runoff generation processes in tropical mature green roof ecosystems

Rainfall retention and runoff detention are likely the most important ecosystem services provided by extensive green roofs (EGRs) that contribute to urban stormwater mitigation and management. However, the hydrological performance and runoff generation mechanisms of mature, well-established EGRs in tropical regions remain poorly understood. This study evaluated the rainfall retention, discharge detention times and processes of runoff generation in two neighbouring 20-year-old EGRs with different slopes (2° and 14° for EGRns and EGRws, respectively) and management practices in Mexico City; results were compared with those obtained in a conventional roof (CR, 2° slope). Precipitation, substrate moisture and storm runoff were continuously measured during the 2017 and 2018 rainy seasons (May–November). Results showed spatial differences in substrate properties and moisture within and between green roofs. In general, higher bulk densities and a wide range of variation in water content characterized the bare substrate areas compared to those below vegetation. Greatest increases in substrate moisture and storm runoff were observed in the steeper green roof. Subsurface flow was the dominant process controlling the amount and timing of stormflow in the EGRs. The occurrence of saturation excess overland flow was small and detected when large rain events were preceded by high wetness conditions. The main factors influencing the hydrological responses of the green roofs were their substrate hydrophysical properties, related mostly to vegetation cover, management and age, and to much lesser extent to slope and substrate depth. On average, rainfall retention was ~60% in the EGRs with significantly longer delays and prolonged runoff times (100 and 340 min, respectively) compared to CR (3%, 20 min, and 258 min, respectively). Overall, these findings highlight the potential of EGRs in reducing stormflow and peak discharges for most rainfall in Mexico City, and thus mitigating the risk of saturation and overflow of urban drainages.     

Evaluation of inundation areas resulting from the diversion of an extreme discharge towards the sea: case study in Tabasco,Mexico

This investigation comprises the hydraulic characterisation of a river located in the Mexican State of Tabasco, including the performance of its flood plain under the action of an extreme river discharge. This is done through the combination of a high‐quality validation dataset, remote sensing information, and a standard 2D numerical model. The dataset was collected during an intensive field campaign that took place in August 2009. In particular, in situ measurements of river discharge, bathymetry, water level, and velocities through a whole tidal cycle are employed along with multi‐spectral satellite imagery. The purpose of this study is twofold. Firstly, the integrated approach comprising the combination of a 2D hydrodynamic model, high‐quality in situ measurements and satellite imagery reduce the uncertainty in the model parameterisation and results. Secondly, it is shown that freely available sources of information, such as the Shuttle Radar Topographic Mission (SRTM) data can be processed and utilized in 2D hydraulic models. This is particularly important in countries where high‐resolution elevation data is not yet available. It is demonstrated that the selected approach is useful when the study of possible consequences in a flood plain induced by an extreme flood discharge are sought. Copyright © 2011 John Wiley & Sons, Ltd.     

Future climate impacts on the hydrology of headwater streams in the Amazon River Basin: Implications for migratory goliath catfishes

Climate-driven alterations of hydro-meteorological conditions can change river flow regimes and potentially affect the migration behaviour of fishes and the productivity of important fisheries in the Amazon basin, such as those for the continental-scale migratory goliath catfishes (Brachyplatystoma, Pimelodidae). In this study, we investigated hydrologic responses to climate change using a hydrologic model forced with climate inputs, which integrate historical (2001–2010) observations and general circulation model (GCM) projections under the emission scenario Representative Concentration Pathway 8.5. We developed an empirical model to characterize future (2090–2099) climate-change impacts on goliath catfish spawning migrations as a function of river flow depth dynamics at the upstream elevational limit of spawning (250 m) in headwater basins of the Amazon. The model results revealed spatially variable impacts of climate change on the catfish spawning migrations. The Marañón, Ucayali, Juruá, Purus, and Madeira basins had a predicted increase in the annual mean (3–8%) and maximum (1.1–4.9%) spawning migration rate (i.e., the fraction of fish that migrate to the spawning grounds in a day), mainly due to the lengthened rising phase of flow-driven migratory events during wet seasons. The Caquetá-Japurá, Putumayo-Içá, Napo, and Blanco rivers had predicted decreases (3–7%) in the mean migration rate because of decreases in the length of the rising season of flow depth and the frequency of migratory events. The predicted timing of fish spawning migrations (quantified by the temporal centroid of migration rates) was delayed by 7–10 days in the west-central and southwest regions and was 8 days earlier in the northwest and northcentral areas, due to changes in the onset of the rising season. We established a river depth baseline that controls the onset of goliath catfish spawning migration. This depth varies between 0.9–5.6 m across study sites. We found that the estimated depth baseline was most sensitive to uncertainties in river width and cross-sectional channel shape. These results may help inform sustainable adaptation strategies for ecosystem conservation and local fisheries management in the Amazon basin.     

Environmental change in the Ría de Vigo,NW Iberia,since the mid‐Holocene: new palaeoecological and seismic evidence

Pollen analyses (pollen, dinocysts and others) were combined with high‐resolution seismic‐stratigraphy sequences to reconstruct environmental dynamics and regional sea‐level (RSL) changes in a ria in NW Iberia. The chronological framework was established using radiocarbon dating and pollen markers that are related to a number of historical events. Major intensifications of the regional upwelling regime occurred during predominant NAO positive stages, dated to c. 4600–4300, 3800–3600, 3200–2700 and 2600–2400 cal. a BP. The regional Early Highstand System Tract spans from before 4500 to c. 3200 cal. a BP. During this period RSL was still rising, but several short episodes of higher terrestrial influence were detected between c. 4300–3800 and 3600–3200 cal. a BP. A readjustment occurred between 3200 and 2300 cal. a BP, including the first stage of relative sea‐level drop (2.8 ka event) dated to 3200–2800 cal. a BP, with the RSL recovering between 2800 and 2300 cal. a BP. The subsequent Later Highstand System Tract, after 2300 cal. a BP, corresponds to a final period of rising sea level that caused the final inundation of San Simón Bay. Since then, only minor changes in relative sea level can be postulated (e.g. towards the end of the Roman Period, in the Middle Ages and during the Little Ice Age). This new evidence is consistent with most of the available palaeoecological and historical information, but it provides a more detailed, near‐complete succession of simultaneous changes occurring in both the terrestrial and the marine ecosystems.     

Major moisture sources for Western and Southern India and their role on synoptic‐scale rainfall events

Although the identification of the moisture sources of a region is of prominent importance to characterize precipitation, the origin and amount of moisture towards the Indian Subcontinent and its relationship with the occurrence of precipitation are still not completely understood. In this article, the origin of the atmospheric water arriving to the Western and Southern India during a period of 5 years (1 January 2000–31 December 2004) is investigated by using a Lagrangian diagnosis method. This methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity of thousands of air particles aimed to the study area following the observed winds. During the summer monsoon, the main supply of moisture is the Somali Jet, which crosses the equator by the West Indian Ocean. The recycling process is the main water vapour source in winter. Two additional moisture sources located over northwestern India and the Bay of Bengal are identified. A 30% increase in the moisture flux from the Indian Ocean has been related to the occurrence of strong precipitation in the area, and at the end of the monsoon, the recycling became a significant contribution to the last part of the wet season of Western and Southern India. Copyright © 2011 John Wiley & Sons, Ltd.     

New evidence for the presence of reindeer (Rangifer tarandus) on the Iberian Peninsula in the Pleistocene: an archaeopalaeontological and chronological reassessment

Reindeer (Rangifer tarandus) populations reached the Iberian Peninsula during the end of the Middle Pleistocene and there are numerous examples of this species from Late Pleistocene Mousterian and Upper Palaeolithic sites. In this paper, new evidence of reindeer in the east Cantabrian region is presented that further supports the timing of this species’ first appearance, and previous assessments are updated. To date, the presence of this species has been identified at 55 sites in the Iberian Peninsula, nearly as many as those of mammoth (Mammuthus primigenius) and woolly rhinoceros (Coelodonta antiquitatis) combined. Most of the sites with presence of reindeer (50) are located in the Cantabrian region with a clear increase in the density of sites and remains towards the Pyrenees. The remaining five sites with evidence of reindeer are located on the other side of the Pyrenees in the NW corner of Catalonia. In contrast, archaeological evidence of reindeer in the form of art (both parietal and portable) is more scarce and scattered. Evidence for the representation of these animals has been found outside the northern fringe of the Iberian Peninsula, which could reflect either long‐distance cultural communication or the movement of human groups.