The aim of the present study is to estimate the export fluxes of major dissolved species at the scale of the Amazon basin, to identify the main parameters controlling their spatial distribution and ...to identify the role of discharge variability in the variability of the total dissolved solid (TDS) flux through the hydrological cycle. Data are compiled from the monthly hydrochemistry and daily discharge database of the “Programa Climatologico y Hidrologico de la Cuenca Amazonica de Bolivia” (PHICAB) and the HYBAM observatories from 34 stations distributed over the Amazon basin (for the 1983–1992 and 2000–2012 periods, respectively). This paper consists of a first global observation of the fluxes and temporal dynamics of each geomorphological domain of the Amazon basin. Based on mean interannual monthly flux calculations, we estimated that the Amazon basin delivered approximately 272 × 10
6
t year
−1
(263–278) of TDS during the 2003–2012 period, which represents approximately 7 % of the continental inputs to the oceans. This flux is mainly made up by HCO
3
, Ca and SiO
2
, reflecting the preferential contributions of carbonate and silicate chemical weathering to the Amazon River Basin. The main tributaries contributing to the TDS flux are the Marañon and Ucayali Rivers (approximately 50 % of the TDS production over 14 % of the Amazon basin area) due to the weathering of carbonates and evaporites drained by their Andean tributaries. An Andes–sedimentary area–shield TDS flux (and specific flux) gradient is observed throughout the basin and is first explained by the TDS concentration contrast between these domains, rather than variability in runoff. This observation highlights that, under tropical context, the weathering flux repartition is primarily controlled by the geomorphological/geological setting and confirms that sedimentary areas are currently active in terms of the production of dissolved load. The log relationships of concentration vs discharge have been characterized over all the studied stations and for all elements. The analysis of the slope of the relationship within the selected contexts reveals that the variability in TDS flux is mainly controlled by the discharge variability throughout the hydrological year. At the outlet of the basin, a clockwise hysteresis is observed for TDS concentration and is mainly controlled by Ca and HCO
3
hysteresis, highlighting the need for a sampling strategy with a monthly frequency to accurately determine the TDS fluxes of the basin. The evaporite dissolution flux tends to be constant, whereas dissolved load fluxes released from other sources (silicate weathering, carbonate weathering, biological and/or atmospheric inputs) are mainly driven by variability in discharge. These results suggest that past and further climate variability had or will have a direct impact on the variability of dissolved fluxes in the Amazon. Further studies need to be performed to better understand the processes controlling the dynamics of weathering fluxes and their applicability to present-day concentration–discharge relationships at longer timescales.
This study presents a methodology for the regional parameters estimation of the SWAT (Soil and Water Assessment Tool) model, with the objective of estimating daily flow series in the Pacific drainage ...under the context of limited hydrological data availability. This methodology has been designed to obtain the model parameters from a limited number of basins (14) to finally regionalize them to basins without hydrological data based on physical-climatic characteristics. In addition, the bootstrapping method was selected to estimate the uncertainty associated with the parameters set selection in the regionalization process. In general, the regionalized parameters reduce the initial underestimation which is reflected in a better quantification of daily flows, and improve the low flows performance. Furthermore, the results show that the SWAT model correctly represents the water balance and seasonality of the hydrological cycle main components. However, the model does not correctly quantify the high flows rates during wet periods. These findings provide supporting information for studies of water balance and water management on the Peruvian Pacific drainage. The approach and methods developed can be replicated in any other region of Peru.
Hydrological changes were assessed considering possible changes in precipitation and regulation or hydraulic diversion projects developed in the basin since 1960s in terms of improving water supply ...of the Rimac River, which is the main source of fresh water of Peru’s capital. To achieve this objective, a trend analysis of precipitation and flow series was assessed using the Mann-Kendall test. Subsequently, the Eco-flow and Indicators of Hydrologic Alteration (IHA) methods were applied for the characterization and quantification of the hydrological change in the basin, considering for the analysis, a natural period (1920–1960) and an altered period (1961–2012). Under this focus, daily hydrologic information of the “Chosica R-2” station (from 1920 to 2013) and monthly rainfall information related to 14 stations (from 1964 to 2013) were collected. The results show variations in the flow seasonality of the altered period in relation to the natural period and a significant trend to increase (decrease) minimum flows (maximum flows) during the analyzed period. The Eco-flow assessment shows a predominance of Eco-deficit from December to May (rainy season), strongly related to negative anomalies of precipitation. In addition, a predominance of Eco-surplus was found from June to November (dry season) with a behavior opposite to precipitation, attributed to the regulations and diversion in the basin during that period. In terms of magnitude, the IHA assessment identified an increase of 51% in the average flows during the dry season and a reduction of 10% in the average flows during the rainy season (except December and May). Furthermore, the minimum flows increased by 35% with shorter duration and frequency, and maximum flows decreased by 29% with more frequency but less duration. Although there are benefits of regulation and diversion for developing anthropic activities, the fact that hydrologic alterations may result in significant modifications in the Rimac River ecosystem must be taken into account.
This study is a geochemical investigation of the Andean and Foreland basins of the Amazon River at high spatial and time resolution, carried out within the framework of the HYBAM research program ...(Hydro-geodynamics of the Amazon Basin). Monthly sampling was carried out at 27 gauging stations located in the upper tributaries of the Amazon Basin (from north to south: the Napo, Marañon, Ucayali, Madre de Dios-Beni and Mamore Rivers). The aim of this paper is to estimate the present-day chemical weathering rate (CWR), as well as the flux of CO₂ consumption from total and silicate weathering in the Andes and Foreland Amazon basins, and to discuss their distribution as a function of geomorphic and structural parameters. Based on the forward method, the Napo and other Ecuadorian basins present high silicate weathering rates in comparison with the other basins. We confirm that the Marañon and Ucayali Rivers control the Amazon hydrochemistry due to the presence of salt rocks and carbonates in these basins. The Madre de Dios, Beni and Mamore basins do not contribute much to the Amazon dissolved load. This north to south CWR gradient can be explained by the combination of decreasing weatherable lithology surface and decreasing runoff rates from the north to the south. The foreland part of the basins (or Mountain–Lowland transition) accounts for nearly the same proportion of the Amazon silicate chemical weathering and carbonate chemical weathering fluxes as the Andean part. This result demonstrates the importance of the sediment accumulation areas in the Amazon Basin weathering budget and can be explained by the occurrence of a higher temperature, the deposition of fresh sediments from Andean erosion and a higher sediment residence time than in the upper part of the basin. With a total CO₂ consumption rate of 744.10³moleskm⁻²year⁻¹ and a silicate CO₂ consumption rate of 300.10³moleskm⁻²year⁻¹, the Upper Amazon River (Andes+Foreland part) is the most intense part of the Amazon Basin in terms of atmospheric CO₂ consumption by weathering processes. It is an important CO₂ sink by weathering processes but accounts for only somewhat more than half of the CO₂ consumption by silicate weathering of the Amazon Basin. This result points out the importance of the Lowland part of the basin in the inorganic C silicate budget. The Upper Amazon accounts for 2–4% of the world's silicate CO₂ consumption, which is the same proportion as for the southern and southern-east Himalaya and Tibetan plateau.
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.
Key Points
Trends depend on latitude and choice of reference period
Recent coastal cooling is consistent with a PDO‐analog model
High‐elevation warming signal outside of 1σ model spread
According to the Peruvian agricultural ministry, the Pacific watersheds where the great cities and intense farming are located only benefit from 1% of the available freshwater in Peru. Hence a ...thorough knowledge of the hydrology of this region is of particular importance. In the paper, analysis of this region and of the two other main Peruvian drainages, the Titicaca and Amazonas are reported. Rainfall and runoff data collected by the Peruvian National Service of Meteorology and Hydrology (SENAMHI) and controlled under the Hydrogeodynamics of the Amazon Basin (HyBAm) project is the basis of this basin-scale study that covers the 1969–2004 period. Beyond the strong contrasting rainfall conditions that differentiate the dry coastal basins and the wet eastern lowlands, details are given about in situ runoff and per basin rainfall distribution in these regions, and about their different altitude–rainfall relationships. Rainfall and runoff variability is strong in the coastal basins at seasonal and inter-annual time scales, and related to extreme El Niño events in the Pacific Ocean. However, rainfall and runoff are more regular in the Andes and Amazonas at the inter-annual time scale. Warm sea-surface temperatures in the northern tropical Atlantic tend to produce drought in the southern Andes basins. Moreover, significant trends and change-points are observed in the runoff data of Amazonas basins where rainfall and runoff decrease, especially after the mid-1980s and during the low-stage season. Almost all the coastal basins show some change in minimum runoff during the last 35 years while no change is observed in rainfall. This means that human activity may have changed runoff in this region of Peru, but this hypothesis deserves more study.Editor Z.W. Kundzewicz; Associate editor Š. BlažkováCitation Lavado C., W.S., Ronchail, J., Labat, D., Espinoza, J.C. and Guyot, J.L., 2012. Basin-scale analysis of rainfall and runoff in Peru (1969–2004): Pacific, Titicaca and Amazonas watersheds. Hydrological Sciences Journal, 57 (4), 625–642.
The present study investigates the application of the index flood L-moments-based regional frequency analysis procedure (RFA-LM) to the annual maximum 24-h rainfall (AM) of 33 rainfall gauge stations ...(RGs) to estimate rainfall quantiles at the Titicaca Lake drainage (TL). The study region was chosen because it is characterised by common floods that affect agricultural production and infrastructure. First, detailed quality analyses and verification of the RFA-LM assumptions were conducted. For this purpose, different tests for outlier verification, homogeneity, stationarity, and serial independence were employed. Then, the application of RFA-LM procedure allowed us to consider the TL as a single, hydrologically homogeneous region, in terms of its maximum rainfall frequency. That is, this region can be modelled by a generalised normal (GNO) distribution, chosen according to the
Z
test for goodness-of-fit, L-moments (LM) ratio diagram, and an additional evaluation of the precision of the regional growth curve. Due to the low density of RG in the TL, it was important to produce maps of the AM design quantiles estimated using RFA-LM. Therefore, the ordinary Kriging interpolation (OK) technique was used. These maps will be a useful tool for determining the different AM quantiles at any point of interest for hydrologists in the region.
Estimating water resources is important for adequate water management in the future, but suitable data are often scarce. We estimated water resources in the Vilcanota basin (Peru) for the 1998–2009 ...period with the semi-distributed hydrological model PREVAH using: (a) raingauge measurements; (b) satellite rainfall estimates from the TRMM Multi-satellite Precipitation Analysis (TMPA); and (c) ERA-Interim re-analysis data. Multiplicative shift and quantile mapping were applied to post-process the TMPA estimates and ERA-Interim data. This resulted in improved low-flow simulations. High-flow simulations could only be improved with quantile mapping. Furthermore, we adopted temperature and rainfall anomalies obtained from three GCMs for three future periods to make estimations of climate change impacts (Delta-change approach) on water resources. Our results show more total runoff during the rainy season from January to March, and temporary storages indicate that less water will be available in this Andean region, which has an effect on water supply, especially during dry season. Editor Z.W. Kundzewicz; Associate editor D. Gerten
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