Positive Precipitation Trends Research Articles

Trends in temperature and precipitation at high and low elevations in the main mountain ranges of the Iberian Peninsula (1894–2020): The Sierra Nevada and the Pyrenees

AbstractThis study describes temperature and precipitation trends in the two National Parks located in the two highest mountain ranges on the Iberian Peninsula: the Sierra Nevada (Sierra Nevada National Park, SN) and the Pyrenees (Aigüestortes i Sant Maurici National Park, ASM). Special focus is placed on analysing disparities between the lowlands and the highlands, as well as the agreement between observational data and grid data (IBERIA01 and E‐OBS). For this purpose, a quality‐controlled and homogeneity‐adjusted database of the daily maximum temperature, minimum temperature and precipitation (SMADS database) has been generated. Regional trends in mean temperature indicate that warming in ASM (0.17°C·decade−1) was greater than in the Sierra Nevada (SN) (0.13°C·decade−1) in the longest joint period, 1930–2020. For annual precipitation, the trends over the past nine decades were negative, although not significantly. Only the summer in SN showed a significant negative trend, which has intensified in recent decades to −13.4%·decade−1 for 1975–2020. A parallel evolution was observed in the annual mean temperature of the highlands (>1500 m) and lowlands (<1500 m) of ASM, with a common trend of 0.17°C·decade−1, while in SN negative elevation‐dependent warming was detected. Differences between lowlands and highlands were also noted in precipitation trends in both mountain ranges: a positive trend in precipitation was found in the lowlands while in the highlands practically null trends (ASM) or decreasing precipitation trends (SN) were detected. The comparison of the Spanish Mountain Adjusted Daily Series (SMADS) results with the IBERIA01 and E‐OBS grid series yielded differences no greater than ±0.2°C·decade−1. No notable differences were detected between the regional trends calculated with observational series or with grid series. These results worsened when the differences in the trends detected in the individual observed temperature series were compared against the corresponding grid series.

Hydroclimatic trends, breakpoints and future projection analysis of the Ogun River Basin in West Africa

Abstract Trend analysis is important to understand the performance and features of hydrological variables over a long-time scale. This study analyses the hydroclimatic trends in precipitation, temperature (minimum and maximum) data from seven synoptic stations and river discharge from three outlets that were investigated between 1984–2019 and projected between 2020–2060 over the Ogun River Basin. The results of the trend analysis showed a non-significant positive trend in precipitation and a significant positive trend (p,0.05 and p,0.01 significant trends) in maximum and minimum temperatures. The discharge reveals a non-significant positive trend on the annual scale while a significant decreasing trend in the dry season. The annual rainfall projection is expected to increase by 1.3% under RCP 2.6 and 1.4% under RCP 8.5 by 2060. The mean annual temperature is expected to increase between 1.5-2.5 °C under RCP 2.6 and 2-3.5 °C under RCP 8.5 by 2060, respectively. The variations in discharge without significant changes in rainfall suggested other variables were influencing the discharge. These could be changes in river basin physical elements such as alterations in the dynamics of land use land cover changes. The findings of this study can be used for strategizing adaptation and mitigation measures for water resources management.

Gross Discrepancies between Observed and Simulated Twentieth-to-Twenty-First-Century Precipitation Trends in Southeastern South America

AbstractSoutheastern South America (SESA; encompassing Paraguay, southern Brazil, Uruguay, and northern Argentina) experienced a 27% increase in austral summer precipitation from 1902 to 2019, one of the largest observed trends in seasonal precipitation globally. Previous research identifies Atlantic multidecadal variability and anthropogenic forcing from stratospheric ozone depletion and greenhouse gas emissions as key factors contributing to the positive precipitation trends in SESA. We analyze multimodel ensemble simulations from phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP) and find that not only do Earth system models simulate positive SESA precipitation trends that are much weaker over the historical interval, but some models persistently simulate negative SESA precipitation trends under historical forcings. Similarly, 16-member ensembles from two atmospheric models forced with observed historical sea surface temperatures never simulate precipitation trends that even reach the lower bound of the observed trend’s range of uncertainty. Moreover, while future twenty-first-century projections from CMIP6 yield positive ensemble mean precipitation trends over SESA that grow with increasing greenhouse gas emissions, the mean forced response never exceeds the observed historical trend. Preindustrial control runs from CMIP6 indicate that some models do occasionally simulate centennial-scale trends in SESA that fall within the observational range, but most models do not. Results point to significant uncertainties in the attribution of anthropogenically forced influences on the observed increases in precipitation over SESA while also suggesting that internal decadal-to-centennial variability of unknown origin and not present in state-of-the-art models may have also played a large role in generating the twentieth-to-twenty-first-century SESA precipitation trend.

Recent Changes in Water Discharge in Snow and Glacier Melt-Dominated Rivers in the Tienshan Mountains, Central Asia

Global warming has generally led to changes in river runoffs fed by snow and glacier meltwater in mountain ranges. The runoff of the Aksu River, which originates in the Southern Tienshan Mountains, exhibited a positive trend during 1979–2002, but this trend reversed during 2002–2015. Through a comprehensive analysis, this study aims to estimate potential reasons for changes in the runoff of its two contrasting headwaters: the Toxkan and Kumalak Rivers, based on climatic data, the altitude of the 0 °C isotherm, glacier mass balance (GMB), snow cover area (SCA), snow depth (SD) and the sensitivity model. For the Toxkan River, the decrease in spring runoff mainly resulted from reductions in precipitation, whereas the decrease in summer runoff was mainly caused by early snowmelt in spring and a much-reduced snow meltwater supply in summer. In addition, the obvious glacier area reduction in the catchment (decreased to less than 4%) also contributed to the reduced summer runoff. For the Kumalak River, a sharp decrease rate of 10.21 × 108 m3/decade in runoff was detected due to summertime cooling of both surface and upper air temperatures. Reduced summer temperatures with a positive trend in precipitation not only inhibited glacier melting but also dropped the 0 °C layer altitude, resulting in a significant increase in summertime SCA and SD, a slowing of the glacier negative mass balance, and a lowering of the snow-line altitude.

Time trend analysis of some agroclimatic variables during the last half century over Iran

We assessed the trends of precipitation, maximum and minimum temperature (Tmax and Tmin), diurnal temperature range (DTR), water requirement of autumn-planted wheat and summer-cropped corn (CWRwheat and CWRcorn), and reference evapotranspiration (ET0) under climate change over Iran using the Mann–Kendall test in 1967–2012. The presence of change-point in the series was also studied by the Pettitt test. In order to determine the length of growing season of autumn-sown crop (GSAC) and growing season of summer-sown crop (GSSC), the temperature-based and soil water-based approaches were employed. The analyses for Tmax, DTR, precipitation, and ET0 series were carried out over the entire year, GSAC, GSSC, mid-GSSC (MGSSC), early GSAC (EGSAC), and late GSAC (LGSAC). Further, the Tmin analysis was performed during the January–February–March (JFM). Precipitation had a negative trend in EGSAC, LGSAC, and GSAC at most stations. However, a positive trend in precipitation was found during MGSSC and GSSC at approximately 74% of cases. An increasing trend was detected for Tmax (except for LGSAC and EGSAC) and Tmin in most investigated locations. Moreover, DTR exhibited a downward trend for most regions except in GSAC. Increased Tmin and reduced DTR, unlike elevated Tmax, seem to have positively influenced autumn-sown crops. At the majority of cases, there was an upward trend in ET0, CWRwheat, and CWRcorn. Such increase in CWR and ET0 appears to have placed pressure on water resources through enhancing irrigation demand. Unlike for precipitation, ET0, and Tmax, a significant change-point occurred within Tmin, DTR, and CWR series for most sites.

Decadal variation in precipitation regime in northwest of Iran

Previous studies revealed that the interannual variation of precipitation in the northwest of Iran (NWI) was controlled mainly by the Mediterranean cyclones and local mechanisms. Drawing upon the literature, the aim of this study is twofold: examining precipitation variability resulting from each of the abovementioned mechanism and investigating variation in precipitation regime in the NWI during 1961–2010. To provide a better understanding of the features of precipitation regime in the NWI, in the present study, I put the spotlight on the changes in precipitation patterns occurring over five decades in a context experiencing climate change. Accordingly, the annual, semiannual, and triple cycle of precipitation data from 1961 to 2010, which were obtained from 250 stations and by which a gridded dataset of monthly precipitation for the period above was created, were analyzed using harmonic analysis. The results showed that the regional average of precipitation during five successive decades decreased from 385.8 mm in the first decade to 297.3 mm in the last decade. The differences in the precipitation values during the five decades under study can be due to the slight positive trends in precipitation in summer and considerable negative trends in other seasons. Moreover, global warming and changes in the path of storm tracks can be considered as the possible reasons behind the observed changes in the precipitation in the NWI.

Interannual and Long-Term Precipitation Variability Along the Subtropical Mountains and Adjacent Chaco (22–29° S) in Argentina

Recent studies documenting climate variability in South America have provided valuable information for understanding current and past dynamics of the climate system. Long meteorological records represent an essential tool to properly characterize climate fluctuations from decadal to multi–decadal scales. Unfortunately, the scarcity of continuous and homogeneous instrumental records is a major constraint to determine long–term variations in South America. Our knowledge of the forcings modulating the hydrological variability in mountains is still limited, despite their importance as freshwater sources for people living in the adjacent piedmonts and lowlands. The objective of this work is to determine the spatial–temporal variability of precipitation in the humid subtropical Andes and the Chaco region in North Western Argentina (NWA). Thirty– four rainfall records covering the common period 1934–1990, partially updated to 2016, were used to extend and identify the dominant patterns of seasonal to annual hydroclimatic variability based on principal components analysis. Intensity and frequency of droughts and pluvials (95th percentiles, respectively) were determined for the dominant patterns of variability. Our results show a positive trend in precipitation since 1970s in all temporal patterns and sub–regions. In addition, precipitation variability (both positive and negative extremes) increases during these last decades. Correlation analysis with sea–surface temperatures and wind anomalies during summer, reveal Amazon moisture sources and large–scale oceanic controls on NWA precipitation. The extended precipitation series shows that the frequency of pluvials has increased since the 1970s interrupted by few extreme droughts. This record can be considered representative of precipitation variations across NWA, including different environments in the Chaco, sub–Andes and Puna.

The Precipitation Trend in Baglung District: A Statistical Analysis

The climate pattern of Nepal is uncertain regarding the precipitation but the extreme events such as floods and drought are increasing. Due to an increase in uncertain precipitation, the extreme rainfall and its intensity are also increased. Baglung District elevated from 650m to 4300m has a diverse climatic zone from upper tropical to alpine, almost similar to the whole Nepal. The data were taken from the Department of Hydrology and Meteorology from 1970 to 2018 (on monthly basis) are used for analyzing the precipitation trends in Baglung District based on five stations by taking the secondary data. To analyze the data, Mann- Kendall, and Sen’s Slope are used to find trend and magnitude. SPSS and R softwere are used to draw graph and other statistical calculations. The analysis shows that there is a positive trend in precipitation in the Baglung district. This is contradictory to national trends of precipitation, which is slightly negative. The maximum value of precipitation is 271.892mm in 1998, followed by 263.070mm in 2000, and the minimum value is 27.217mm in 1973, followed by 86.10 mm in 1972. There is a wide variation in average monthly rainfall in different stations ranging from 158.326mm (Baglung station) to 235.828mm (Rangkhani station) with standard deviations 199.342mm and 310.196mm respectively. The analysis indicates that the trend of precipitation is slightly positive but insignificant which shows that the intensity of rainfall is increased, but the number of rainy days is decreased. Similarly, the results indicate that the average rainfall in Baglung (190.400mm) is higher than the national level (150mm app.).

Global warming, desertification/degradation, and droughts in arid regions

Applications of the concept of climatic desertification are considered. They include an approach to a separate assessment of aridization and degradation of arid lands and an approach to identifying “islands” of desertification from satellite data. It is established that the contribution of anthropogenic land degradation to desertification is confirmed by a significant linear trend of interannual fluctuations of satellite indicators of pasture digression in all the studied arid areas of Russia and Mongolia in the period 2000–2016. Significant trends in the intensification of aridization were characteristic only for a part of arid areas. Because of the excessive pastoral digression in arid areas, “islands” of desertification of anthropogenic origin are formed. The lifetime of such “islands” is determined by human influence and fluctuations in the humidity of the climate. An additional factor in the short-term decline in the life of the “islands” in Mongolia is the catastrophic death of livestock as a result of natural disasters (drought, zuta). The “island” of desertification, of natural origin, is found in the reserved part of the Sonora Desert, where rainy seasons and droughts determine the spread of aridization. Particular attention is paid to the analysis of trends in climatic characteristics. The increase in air temperature occurred in all the areas under study. Negative trends in annual and seasonal precipitation dominated the steppe zone of Russia during the periods 1936–1960 and 1991–2016, when the surface temperature of the North Atlantic was above normal. On the contrary, positive precipitation trends, weakening aridization, were observed in the period 1961–1990, corresponding to a temperature below the norm.

Southern Hemisphere subtropical drying as a transient response to warming

Climate projections1–3 and observations over recent decades4,5 indicate that precipitation in subtropical latitudes declines in response to anthropogenic warming, with significant implications for food production and population sustainability. However, this conclusion is derived from emissions scenarios with rapidly increasing radiative forcing to the year 21001,2, which may represent very different conditions from both past and future ‘equilibrium’ warmer climates. Here, we examine multi-century future climate simulations and show that in the Southern Hemisphere subtropical drying ceases soon after global temperature stabilizes. Our results suggest that twenty-first century Southern Hemisphere subtropical drying is not a feature of warm climates per se, but is primarily a response to rapidly rising forcing and global temperatures, as tropical sea-surface temperatures rise more than southern subtropical sea-surface temperatures under transient warming. Subtropical drying may therefore be a temporary response to rapid warming: as greenhouse gas concentrations and global temperatures stabilize, Southern Hemisphere subtropical regions may experience positive precipitation trends. Warming is altering subtropical precipitation; however, it is not clear whether this will continue in an equilibrium climate. Using projections to 2300, Southern Hemisphere drying is shown to be a transient response to the meridional temperature gradient changes.

Spatio-temporal variability of drought and effect of large scale climate in the source region of Yellow River

The effects of drought, a devastating natural disaster, have expanded due to intense global warming. Therefore, studying the spatio-temporal evolution and formation mechanism of drought is urgent and important. In this paper, the standardized precipitation evapotranspiration index (SPEI) of the source region of Yellow River was calculated for the years 1961–2015, and the heuristic segmentation and Modified Mann-Kendall methods were used to study the change points and trends of precipitation, temperature, and SPEI. The empirical orthogonal function was used to study the major modes of the SPEI, and cross wavelet analysis was used to demonstrate the relationship between SPEI and large-scale climate factors. The results initially demonstrated no change point and an insignificant positive trend in precipitation. Temperature revealed a significant increasing trend, and a change point was detected in 1997. SPEI indicated a change point in 1993, and a significant increasing trend was observed thereafter. These findings reveal that drought in the study area is highly related to the El Niño-Southern Oscillation. The North Atlantic and Arctic oscillations caused similar impacts on drought. By comparison, changes in SPEI were slightly related to the Pacific decadal oscillation. These results provide useful information for evaluating drought changes in the study area, early warning of drought, and water resource management.

A database of water and heat observations over grassland in the north-east of Japan

Abstract. A highly valuable database of long-term hydrometeorological measurements is presented, containing in situ observations for a period of 37 years from a well-maintained grassland in the north-east of Japan. The observations include shortwave radiation, net radiation, air and dew point temperatures at three elevations, soil temperature at four depths, sensible heat flux, soil heat flux, wind speed, relative humidity, air pressure and precipitation. The heights of measurements are 1.6, 12.5 and 29.5 m above ground, with the soil-layer observations at depths of 0.02, 0.1, 0.5 and 1 m. This high-quality database includes four temporal resolutions of 10 s, 0.5 h, 1 h and 24 h, with the hourly data presented here. Monthly and annual statistics are presented at the database web page of the Center for Research in Isotopes and Environmental Dynamics and Prediction of the University of Tsukuba, http://doi.org/10.24575/0001.198108. We validated the data by comparing them with published data from the local meteorological agency in Tateno operated by the Japan Metrological Agency, including the average, maximum and minimum values of air temperature, shortwave radiation, wind speed, relative humidity and precipitation. We have generated a daily downward longwave radiation time series with a method developed by Kondo and Xu (1997) based on the observations from the database. This constructed time series agrees well with observations collected between 2002 and 2006, as evaluated based on the values of the Nash–Sutcliffe efficiency (=0.947) and percent bias (=1.486). For the whole database, annually averaged values show a positive trend in precipitation, air temperature, shortwave radiation, net radiation and sensible heat flux over the past 37 years, with a negative trend detected for wind speed, soil heat flux and soil temperature.

Trends in daily precipitation in highlands region of Santa Catarina, southern Brazil

This study evaluates the occurrence of trends in time series of precipitation in the highlands region of Santa Catarina, Southern Brazil. Daily precipitation data of three weather stations at Lages, São Joaquim and Campos Novos were used to evaluate rainfall trends. The trends were analyzed through the Seasonal Mann Kendall test, to include occurrence of maximum annual 1-day precipitation (RX1), maximum annual consecutive 2-day precipitation (RX2) and maximum annual consecutive 3-day precipitation (RX3) and evaluation of Rainfall Anomaly Index (RAI). Trends were identified in two of three weather stations investigated. Positive precipitation trends were found in the spring and winter for Lages, and in the spring and summer for São Joaquim. Also, there is a trend of increase in the RX1, RX2 and RX3 frequencies and an increase in positive anomalies in the last decade for these stations. There are no statistically significant trends in the precipitation of Campos Novos, which may be associated with the short series of available data for the analysis. The occurrence of El Niño phenomenon with moderate to strong intensity was usually associated with the occurrence of positive precipitation anomalies and the La Niña phenomenon was related to the occurrence of negative anomalies. However, the influence of La Niña in the periods of negative anomaly has been reduced since the beginning of the 21st century.

Comparison of Arctic sea ice thickness and snow depth estimates from CFSR with in situ observations

Sea ice growth is modulated by snow cover, and understanding this relationship requires an accurate determination of snow depth. However, a lack of in situ measurements complicates understanding of the interaction of snow depth with sea ice growth. We evaluated the accuracy of Climate Forecast System Reanalysis (CFSR) data for snow depth and sea ice thickness to study the change of snow depth on Arctic sea ice. We compared CFSR and snow depth data from 35 drifting buoys in 2002–2013. The mean annual cycle of CFSR snow depth corresponded well with the buoy data. However, the CFSR data had a positive bias during winter (10–20 cm) and spring (5–25 cm), and a negative bias during summer (−25–0 cm) and autumn (−5–10 cm). The CFSR data showed increases in snow depth from 1979 to 2013 over the Beaufort and northern Chukchi Seas during November. Significant positive trends in precipitation contributed to increased snow depth in this region when sea ice began to form. The results of model experiments using a 1-D thermodynamic sea ice model in the CFSR demonstrated a recommended value of snow thermal conductivity (0.16 W m−1 K−1), and suggested that the sea ice growth was effectively restricted by the recent increase in snow depth on thin ice during winter.

Austral summer precipitation interannual variability and trends over Southeastern South America in CMIP5 models

ABSTRACTThe purpose of this study is to assess the ability of Coupled Model Intercomparison Project 5 (CMIP5) models in reproducing the variability and change of the austral summer precipitation observed in Southeastern South America (SESA) along the 20th century and beginning of the 21st. Models show a reduction in mean precipitation biases and inter‐model dispersion, and a significant improvement in the representation of the leading pattern of precipitation interannual variability (EOF1), in comparison with Coupled Model Intercomparison Project 3 (CMIP3) models. Changes of the EOF1 activity in the present climate, as represented by both, climate model simulations and rainfall gridded datasets, evidence an increase of the frequency of EOF1 positive events (associated with positive precipitation anomalies in SESA and negative ones in the South Atlantic Convergence Zone) and a decrease of the frequency of EOF1 negative events. Nevertheless there are still large uncertainties due to model differences and the internal variability of the climate system. In order to reduce the impact of model uncertainties, an ensemble of the climate simulations that represent better the features associated with EOF1 activity was built, regardless to which model they correspond. The results obtained with this ensemble confirm that largest precipitation trends in SESA are those represented by climate simulations associated with an increase (decrease) of EOF1 positives (negative) events. It was also found that positive precipitation trends in SESA resulted from climate simulations forced by anthropogenic sources are the largest and significantly different from those from simulations forced by natural sources only, which are not significantly different from zero.

Trends in monthly precipitation over the northwest of Iran (NWI)

Increasing global temperatures during the last century have had their own effects on other climatic conditions, particularly on precipitation characteristics. This study was meant to investigate the spatial and temporal monthly trends of precipitation using the least square error (LSE) approach for the northwest of Iran (NWI). To this end, a database was obtained from 250 measuring stations uniformly scattered all over NWI from 1961 to 2010. The spatial average of annual precipitation in NWI during the period of study was approximately 220.9–726.7 mm. The annual precipitation decreased from southwest to northeast, while the large amount of precipitation was concentrated in the south-west and in the mountainous areas. All over NWI, the maximum and minimum precipitation records occurred from March to May and July to September, respectively. The coefficient of variation (CV) is greater than 44 % in all of NWI and may reach over 76 % in many places. The greatest range of CV, for instance, occurred during July. The spatial variability of precipitation was consistent with a tempo-spatial pattern of precipitation trends. There was a considerable difference between the amounts of change during the months, and the negative trends were mainly attributed to areas concentrated in eastern and southern parts of NWI far from the western mountain ranges. Moreover, limited areas with positive precipitation trends can be found in very small and isolated regions. This is observable particularly in the eastern half of NWI, which is mostly located far from Westerlies. On the other hand, seasonal precipitation trends indicated a slight decrease during winter and spring and a slight increase during summer and autumn. Consequently, there were major changes in average precipitation that occurred negatively in the area under study during the observation period. This finding is in agreement with those findings by recent studies which revealed a decreasing trend of around 2 mm/year over NWI during 1966–2005.

Temperature and Precipitation Variability and Its Effects on Streamflow in the Upstream Regions of the Lancang–Mekong and Nu–Salween Rivers

Abstract Hydrological regimes of alpine rivers are highly sensitive to climate variability/change. Temperature and precipitation variability and its effects on streamflow in the upstream regions of the Lancang–Mekong River (LMR) and Nu–Salween River (NSR) are examined in this study based on long-term observational data from 16 meteorological stations and 2 hydrological stations between the 1950s and 2010. This study employs the Mann–Kendall nonparametric test, together with the trend-free prewhitening (TFPW) approach to test trends and the Breaks For Additive Season and Trend (BFAST) method to detect abrupt changes in the hydrometeorological time series. The relations between air temperature, precipitation, and streamflow trends are assessed using random forest regression. The results show significant climate warming and related prevalent positive precipitation trends both at the annual and seasonal scale. A substantial precipitation increase paralleling climate warming, especially in spring, was also observed. However, no consistent abrupt change in meteorological time series was found. The increasing trends of streamflow with climate warming are seen both for the outlets of the LMR and NSR upstream regions, with the abrupt changes occurring in the mid-1960s and the late 1990s, respectively. The relation of streamflow to annual and wet season precipitation is pronounced, especially for the upstream region of the LMR with a percent variance explained of more than 65%. However, the relatively minor linkage of streamflow to air temperature and dry season precipitation may be confounded by the climate warming–driven changes in snowpack, permafrost, glacier, and evapotranspiration. These results could provide further a reference for the regional water resources management under climate change scenarios.

Long-Term Precipitation Trends in Eastern Slovakia

The objective of this study was to investigate precipitation trends in climatic stations in eastern Slovakia. We investigated 20 climatic stations in Slovakia. The studied period was from 1981 to 2010. Monthly precipitation trends were detected by nonparametric MannKendall statistical test. Positive trends of annual as well as monthly precipitation were found in the analyzed rainfall gauging stations in eastern Slovakia. March was observed to have the highest decreasing trends. All other months displayed mostly increasing trends. In quartile research mostly the summer period shows positive trends in precipitation. In conclusion, Slovakia has an increasing trend of precipitation time series.

Exploring possible connections between hydrological extreme events and climate change in central south Chile

Motivated by recent extreme flow events in the Mataquito River located in the Mediterranean region of Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow, precipitation and temperature within the basin. For the period 1976–2008, positive trends in temperature were observed, especially during spring and summer months. At the same time, we found negative trends in the frequency and intensity of precipitation, especially during spring months. We observed an increasing difference between average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is caused by larger flows during autumn months, although no positive precipitation trends are observed for these months. Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration of high-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen during autumn months, and are associated with high precipitation and high minimum temperatures. Based on a simple assessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem not to be as relevant to the detected flow trends. All these results are in accord with future climate change scenarios that show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation. Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifying also a fate that may be shared by other similar basins in Chile and in other regions of the world.Editor Z.W. KundzewiczCitation Vicuña, S., Gironás, J., Meza, F.J., Cruzat, M.L., Jelinek, M., Bustos, E., Poblete, D., and Bambach, N., 2013. Exploring possible connections between hydrological extreme events and climate change in central south Chile. Hydrological Sciences Journal, 58 (8), 1598–1619.

Hydrological modelling of the Iberá Wetlands in southeastern South America

Summary The Ibera Wetlands are one of the largest inland freshwater ecosystems in the world hosting several unique flora and fauna species. They are located in northeastern Argentina, a region in southeastern South America that experienced large positive precipitation trends during the last decades. The aim of this paper is to calibrate and evaluate a hydrological model on the Ibera basin in order to quantify the hydrologic impacts of potential regional temperature and precipitation variations in the context of climate change as a result of anthropogenic greenhouse gas emissions. For this purpose, a version of the Variable Infiltration Capacity (VIC) hydrological model, accounting for the presence of lakes and Wetlands, was applied for the first time to the Ibera basin. Results show that the model can successfully simulate the main features of the system dynamics, including the daily mean streamflow of the Corriente River, the daily level of the Ibera Lake and the daily lake evaporation. Inclusion of the lake and Wetlands module improved the streamflow simulations. Sensitivity tests of the Ibera basin hydrology were performed by varying regional temperature and rainfall conditions according to the outputs of a set of climate models for three different time slices during the 21st century. These tests showed a strong dependence of the basin hydrology on the precipitation changes rather on the temperature ones.