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Urban stormwater quality has been sampled and chemically analyzed in the city of Arequipa, southern Peru. Stormwater samples generated from a 0.04 km2 drainage area in a downtown location were collected during two rainy seasons (2022 and 2023), including both first flush and peak flow for each storm event, analyzing physical and chemical (metals) variables. Results were compared with Peruvian agricultural irrigation standards, identifying also temporal changes and statistical correlations. Several metals (B, Cu, Fe, Mn, and Zn) were detected at concentrations above Peruvian MPLs, with B being the analyte that violated the norm more often. Most pollution occurred at the beginning of each rainy season and during the first flush stages. All vehicle-related contaminants were well correlated except for Pb and Se, which were assumed to have a different source of origin. We recommend that further investigations should focus on the effects of urban stormwater on downstream ecosystems in Peru. Similarly, we strongly recommend the creation of new regulations that ensure proper stormwater quality released from urban areas of this country, as well as preventive/treatment practices to minimize the pollution of downstream aquatic ecosystems and ensure healthy water to irrigate crops located downstream from cities.

The curve illustrates how greenhouse gas concentrations have increased tremendously over the last few decades-increases that are directly correlated with world population growth, subsequent growth in the consumption of energy and fossil fuels, and subsequent reductions in forested areas worldwide. The evolution of total forest cover by hemisphere is illustrated in Figure 2, showing the alarming loss of forests in the southern hemisphere and the slight increase in forest biomass in the northern hemisphere since 1990. [...]the difference in forest cover between the hemispheres has increased from 936 million acres in 1990, to 1,418 million acres in 2010 (FAO 2012).

This study aims to determine if there is variation in precipitation concentrations in Chile. We analyzed daily and monthly records from 89 pluviometric stations in the period 1970–2016 and distributed between 29°12′ S and 39°30′ S. This area was divided into two climatic zones: arid–semiarid and humid–subhumid. For each station, the Gini coefficient or Gini Index (GI), the precipitation concentration index (PCI), and the maximum annual precipitation intensity in a 24-h duration were calculated. These series of annual values were analyzed with the Mann–Kendall test with 5% error. Overall, it was noted that positive trends in the GI are present in both areas, although most were not found to be significant. In the case of PCI, the presence of positive trends is only present in the arid–semiarid zone; in the humid–subhumid zone, negative trends were mostly observed, although none of them were significant. Although no significant changes in all indices are evident, the particular case of the GI in the humid–subhumid zone stands out, where mostly positive trends were found (91.1%), of which 35.6% were significant. This would indicate that precipitation is more likely to be concentrated on a daily scale.

Forest ecosystems play an important role in hydrological processes as surface and subsurface runoff, as well as the storage of water at the catchment scale. Therefore, it is important to have a greater understanding of the effects of forests in the long-term water balance of Mediterranean catchments. In this sense, this study evaluates the effect of native forests, forest plantations, and the combination of both, on long-term streamflow variations in central Chile, an unusual area of Mediterranean climate characterized by a well-marked annual cycle with dry summers and wet winters. Thus, the temporal pattern of monthly streamflow was evaluated for mean flow (Qmean), maximum flow (Qmax), and minimum flow (Qmin) in 42 large-scale (>200 km2) Mediterranean catchments. Each series of monthly streamflow data was QA/QC, and then evaluated using the Mann–Kendall’s non-parametric statistical test to detect temporal variations between 1994 and 2015. In addition to the previous analysis, the monthly series were grouped into wet seasons (April–September) and dry seasons (October–April), to determine if there were any significant differences within the annual hydrological cycle. The areas covered with native and forest plantations and their relative changes were evaluated for each catchment through streamflow variations and forest cover indicators. Results revealed that streamflow variations are positive and significant when more forest cover exists. The intra-catchment relationships assessed for both species revealed the significant role of native forests and mixed masses as key ecosystems for the long-term conservation of summer streamflow in Mediterranean catchments of central Chile. These findings encourage an urgent need to create highland afforestation programs on degraded areas of central Chile, to maximize water storage in a region that is quickly drying out due to unsustainable water and land use management practices and the effects of global warming.

Estimating intensity−duration−frequency (IDF) curves requires local historical information of precipitation intensity. When such information is unavailable, as in areas without rain gauges, it is necessary to consider other methods to estimate curve parameters. In this study, three methods were explored to estimate IDF curves in ungauged areas: Kriging (KG), Inverse Distance Weighting (IDW), and Storm Index (SI). To test the viability of these methods, historical data collected from 31 rain gauges distributed in central Chile, 35° S to 38° S, are used. As a result of the reduced number of rain gauges to evaluate the performance of each method, we used LOOCV (Leaving One Out Cross Validation). The results indicate that KG was limited due to the sparse distribution of rain gauges in central Chile. SI (a linear scaling method) showed the smallest prediction error in all of the ungauged locations, and outperformed both KG and IDW. However, the SI method does not provide estimates of uncertainty, as is possible with KG. The simplicity of SI renders it a viable method for extrapolating IDF curves to locations without data in the central zone of Chile.

The availability of water in Chile has shown signs of decline in recent decades. This is problematic because Chile’s economy depends on mining, forestry, and agricultural activities, all limited by the availability of water resources. In this study, daily, monthly and annual flows in 31 basins located in the arid–semiarid zones (29°12′ S–33°58′ S) and in the humid–subhumid zones (34°43′ S–38°30′ S) of Chile were evaluated using the Mann–Kendall trend test and the quantile–Kendall procedure during three periods: 1984–2021 (31 stations), 1975–2021 (20 stations), and 1969–2021 (18 stations). Results showed that, at the annual level, trends were predominantly negative in both climatic zones and over the three periods analyzed. In the arid–semiarid zone, a higher frequency of annual significant negative trends was found in maximum flows in 1969–2021 and 1975–2021, compared to the last period under study. The humid–subhumid zone showed significant annual negative trends in all series analyzed. At the monthly level, on the other hand, the arid-semiarid zone showed a decrease in significant negative trends as the number of years analyzed increased, for all flow types. The humid–subhumid zone did not indicate a similar defined pattern. Likewise, the quantile–Kendall procedure showed a reduction in the significant trends as the length of the time series was increased in the arid-semiarid zone, but no such pattern was observed in the humid–subhumid zone. Furthermore, a relationship was observed for the PDO and the summer month flows for both zones. Consequently, it is concluded that the flow trends are generally negative, and their statistical significance depends on the period studied.

Access to accurate spatio-temporal groundwater level data is crucial for sustainable water management in Chile. Despite this importance, a lack of unified, quality-controlled datasets have hindered large-scale groundwater studies. Our objective was to establish a comprehensive, reliable nationwide groundwater dataset. We curated over 120,000 records from 640 wells, spanning 1970-2021, provided by the General Water Resources Directorate. One notable enhancement to our dataset is the incorporation of elevation data. This addition allows for a more comprehensive estimation of groundwater elevation. Rigorous data quality analysis was executed through a classification scheme applied to raw groundwater level records. This resource is invaluable for researchers, decision-makers, and stakeholders, offering insights into groundwater trends to support informed, sustainable water management. Our study bridges a crucial gap by providing a dependable dataset for expansive studies, aiding water management strategies in Chile.

Dry-weather flows in urban channels and streams, often termed “urban drool”, represent an important source of urban surface water impairment, particularly in semi-arid environments. Urban drool is a combination of year-round flows in urban channels, natural streams, and storm-sewer systems (runoff from irrigation return flow, car washes, street cleaning, leakage of groundwater or wastewater into streams or storm sewers, etc.). The purpose of this study was to better understand the extent and sources of urban drool pollution in Denver, Colorado by identifying relationships between urban catchment characteristics and pollutants. Water-quality samples were taken throughout Denver at urban drainage points that were representative of a variety of urban characteristics. Samples were analyzed for total suspended solids (TSS), coliforms, Escherichia Coli (E. coli), nutrients (nitrate, phosphorus, and potassium), dissolved and total organic carbon, and dissolved and total recoverable metals. Results from this study were as follows: (1) most contaminants (nitrate, phosphorus, arsenic, iron, manganese, nickel, selenium, and zinc) were concluded to be primarily loaded from shallow groundwater; (2) anthropogenic effects likely exacerbated groundwater pollutant concentrations and contributions to surface water; (3) nitrate, nickel, and manganese may be partially contributed by industrial inputs; (4) medical marijuana cultivation sites were identified as a potential source of nutrient and zinc pollution; (5) E. coli was a ubiquitous contaminant in all urban waterways; (6) erosion of contaminated urban soils, presumably from construction, was found to significantly increase concentrations of TSS, total phosphorus, and total metals. Increasing urbanization and predicted drier climates suggest that dry-weather flows will become more important to manage; the results from this study provide insight on dry-weather water quality management for the City and County of Denver.

Located southwest of the city of Santiago (Chile), the Aculeo Lagoon used to be an important body of water, providing environmental, social, and economic services to both locals (mostly drinking water and small-scale agricultural irrigation) and tourists who visited the area for fishing, sailing, and other recreational activities. The lagoon dried completely in May of 2018. The phenomenon has been attributed to the current climatic drought. We implemented and calibrated a surface-groundwater model to evaluate the hydrogeologic causes of the lagoon’s disappearance, and to develop feasible solutions. The lagoon’s recovery requires a series of urgent actions, including environmental education and significant investment in infrastructure to import water. Ultimately, there are two goals: bringing back historic water levels and ensuring the sustainability of water resources at the catchment scale.

Land surface temperature (LST) is one of the most important variables in the physical processes of surface energy and water balance. The temporal behavior of LST was analyzed between the latitudes 32°00′ S and 34°24′ S (Valparaíso and Metropolitana regions of Chile) for three summer months (December, January, and February) in the 2000–2017 period, using the Terra MODIS image information and applying the Mann–Kendall test. The results show an increase in LST in the study area, particularly in the Andes mountain range in January (5240 km2), which mainly comprises areas devoid of vegetation and eternal snow and glaciers, and are zones that act as water reserves for the capital city of Santiago. Similarly, vegetated areas such as forests, grasslands, and shrublands also show increasing trends in LST but over smaller surfaces. Because this study is regional, it is recommended to improve the spatial and temporal resolutions of the images to obtain conclusions on more local scales.