It is well documented that climate change is growing the occurrence of droughts in many regions that may affect water resources through their water quality and quantity. Nevertheless, in Chile the information is scarce about how water quality of high flow rivers response to droughts. This paper seeks to investigate the effect of an unprecedented mega-drought (2010-2015) on the water quality of Biobío river (36°45′ – 38°49′S and 71º00′ – 73º20′W) Central Chile, one of the largest Chilean rivers that provides abundant freshwater for human consumption, irrigation and hydropower. The water quality (surface water temperature, pH, dissolved oxygen, electrical conductivity, BOD5, suspended solids major ions such as chloride, sodium, nutrients and heavy metals), during the mega-drought (2010-2015) was compared with the water quality from a non-drought period (2000-2009) in two reaches (upstream and downstream) of the river, and we investigated differences in physicochemical parameters in both reaches. Mann-Kendall and seasonal Mann-Kendall trend analyses and Theil-Sen estimator were used to investigate trends of the reaches. Results show during the mega-drought a slightly decrease trend in pH, nutrients (NO2-, NH4+, NO3-, Total P) and suspended solids, and an increase trend in surface water temperature and trace metals (Cr, Fe and Co) in both reaches, mainly during summer, although in winter were also changes found. During the mega-drought, upstream variability suggested more constant concentrations in nutrients and metals than downstream. Based on calculated slopes of major ions and metals trends, during summer seasons more rapid decreasing trends were present than in winters, mainly downstream. These results suggest that seasonal changes in surface water temperature, discharge and precipitation may have some negative changes on water quality content. These highlight that seasonal changes and a progressive reduction of river flow availability affecting the vulnerability of the water quality in this key Chilean river. The outcomes from this research are expected to support and influence actions for policy making to address water quality goals in watershed river management. Hence, to better guide future management and take into account the effects of a river discharge reduction under low flow conditions as a consequence of more frequent drought periods.
<span title="\"En" la="" parte="" donde="" se="" ingresa="" mayor="" de="" las="" descargas,="" cuenta="" con="" cerca="" 40="" ha="" tule,="" que="" bien="" manejado="" puede="" ser="" utilizado="" como="" un="" humedal="" natural="" para="" el="" mejoramiento="" calidad="" agua="" entra="" a="" laguna.\"="">Cajititlan Lake is the second largest lake in Jalisco, located in Tlajomulco´s municipality, with an approximate surface of 2000 ha. It is a shallow lake with an average depth of 3 m. The lake has been impacted for many years from different anthropogenic pressures as water mangement for irrigation and discharge of untreated sewage. This pollution has dramatic effects on lake and has affected the biodiversity in it, having also an important economic impact for inhabitats of the local comunities. From 2009, started presenting massive deaths of fish, and continuing repeted in 2010,2011, 2013 and in a more striking way in september 2014 with the death of almost 200 tons of fish. The lake is located in a closed basin, so all management done in upper areas have impact in water quantity and quality of the lake. The aim fo this research was to find the spatial distribution of pollutants and identify the source of origen using a geographic information system. During the period of september 2014 to september 2016 a monthly water quality monitoring was conducted with 61sampling sites established throughout the lake, to let us know the spatial and temporal distribution of pollutants. The sampling a depths 0.5 m and 1.5 m was made and measured with a multiparameter, the concentration of dissolved oxygen, electrical conductivity, pH, temprature, potential redox and turbidity. Besides water deph and visibility using Secchi disk. The results show a significant variation in oxygen concentration across the lake, keeping the area near downloading an anoxic zone, and other areas where the daily dynamics of oxygen can be moved from near zero to supersaturation during the day by the process of photosynthesis by abundant green algae found as a product of euthropication process. The visible Secchi disk depth is jut 10 to 12 cm resulting in this an indicator of high level of eutrophication. pH values averaged values greater tha 9 units in virtually all sampling sites, giving high alkaline values. the comparisonof the result achieved in dry and rainy indicate that eh anoxic zones moves during rainy season by growing runoff income from the southwest of the lake. Moving wastewater to mayor part of lake in a short time, we thing is the cause of fish kill. Stategies for pollution control should begin from zero discharge of untreated wastewater entering the Cajititlan lake. In zone where there is deposited most of unloads, there are about 40 ha of Typha, that well.managed can be used as a natural wetland to improve the quaity of water entering the Cajititlan lake.
The project goal is to have a diagnosis of water quality of a transboundary river that receives contributions from municipal wastewater with or without treatment, as well as water for agricultural returns that can affect water quality in the Lower Rio Grande, then water quality model. The project is supported with Conagua-Conacyt Sector Funds.
The goal was covered done in the dry season four samples at 15 sites in the main river channel, two tributaries (river Alamo and San Juan), five agricultural drains and 10 discharge of wastewater, including effluent treatment plants located in the section from the dam downstream of Falcon International to the mouth of the Rio Grande to the Gulf of Mexico. About 80 chemical and microbiological parameters, including regulations (NOM-001-SEMARNAT-1996) for wastewater discharges to receiving body and pesticides in the river and tributaries were analyzed.
The Lower Rio Grande is classified as a water body Type B with urban public use so that concentrations obtained from the physico-chemical, microbiological parameters, pesticides and heavy metals were compared with the guidelines of water quality for use 1 set out in the Federal law.
The results indicated that river dissolved oxygen in all cases values greater than 4 mgL-1 were presented considered suitable for use 1 and protection of aquatic life. While total dissolved solids total phosphorus and sulfur, everywhere river and tributaries exceeded the guideline. In April 2016 discharges of effluent treatment plants in Ciudad Mier, Ciudad Camargo and Reynosa 2 did not meet the maximum allowable limit (MAL) of 75 mgL-1 BOD and 200 mgL-1 of COD; Fats and Oils plant Miguel Aleman and Camargo (MAL 15 mgL-1); Fecal coliform plants Nuevo Guerrero, Camargo and Reynosa 2 (1000 MPN/100 mL). The contribution of organic matter, measured as BOD ranged from 1.9 to 36 ton/day. No pesticides were detected.
The results allow zoning of the main sections of the river that receive inputs of pollutants such as El Anhelo Dren where necessary management actions to control pollution because it receives the discharge of the WWTP Reynosa 1 and Escondida Lagoon and that through a monitoring program and surveillance actions to be implemented to improve treatment systems or failing properly operate them to always comply with the regulations. Management must include the participation of the United States, to assess their discharges because the American side have seven treatment plants that discharge to the Lower River Bravo/Grande.
A Multidisciplinary methodology that describes the watershed management of the Laguna de Tuxpan through the climate, topography, geology, soil, vegetation and land use through GIS. The topography showed a maximum altitude of 1731 m. The bathymetry at a height of 749.57 m, indicating a capacity of 18.89 Mm3, an area of 4.1 Mm2 and a maximum depth of 7.86 m. The physicochemical and environmental parameters of 26 sampling sites in the watersheds of the Tuxpan lagoon and Tomatal river, show the generation of 107.01 kg of nitrogen per year, of which 24.54 kg per year are by point sources (22.93%) and 82.41 kg annually are by diffuse sources (77.07%). The quantification of sediment production, indicate that the basin of Tomatal river produces 18.7 tonnes of sediment on the regions of average sloping, this equates to a lost of 7.45 t ha-1 on average throughout the basin. The physicochemical analysis, transparency and chlorophyll-a in the surface and bottom in the season rainy and dry indicate that the water quality is within the maximum permissible limits for the development of aquatic life of Flora and fauna. By the physicochemical characteristics, the lake is classified as warm water body and tropical shallow, with a holomíctic blend, characterizing it as a water body mesotrophic - eutrophic, with tendency to eutrophication through plankton community. The pollution and toxicity by Vibrio fischeri, Daphnia magna, Selenastrum capricornutum y Microcistina was not present in the lake. However, the presence of six types of phthalates, plus the incidence of herbicide atrazine in the lake, point out as source of pollution to the trash of the area and agricultural activity. The wastewater discharges of the river and shore of the lake shown a contamination by the presence of fecal coliform and total suspended solids of natural origin from the watershed from Tuxpan lagoon and the Tomatal river. Therefore, is proposed a strategic plan with objectives, activities, cost and a list of governmental organizations, ONG's, universities, that could give assistance and economic recourses to support the plans recuperation of the most sites degraded in the watersheds, with respect to:1) sites with farming more intense, 2) a program of promotion and adoption of conservation practices for hillside land, 3) construction of little dams within channels for the control sediment and runoff infiltration to help the recharge the aquifer, 4) the river corridor recovery through of reforestation, and 5) control of less polluting chemicals, 6) reorganization of touristic activities 7) control invasive species in the lake, 8) reorganization of fishers activities, 9) programs for social participation to conduce better practice of the water urban residuals.