Previous knowledge on Lake Titicaca

What do we knew when we initiatied this OLT observatory? and what were we missing?

Prepared by Xavier Lazzaro (BOREA/IRD)

At the start of the OLT observatory project, we had a good research base on the ecology and limnology of Lake Titicaca. However, most knowledge came from the Major Lake ('Lago Mayor'), but no permanent long-term monitoring program existed on representative areas for understanding how the trophic state of the lake evolved during the last four decades as a consequence of the combined effects of climate change and human activities. This justifies why we implemented this first observatory project on the highest Large Lake of the world (i.e. one of those 253 lakes larger than 500 km2; Herdendorf 1982). The most relevant works are: the state of the art on eutrophication in the shallow Puno Bay (Northcote et al. 1991); the reference of historical multidisciplinary knowledge on Lake Titicaca (Dejoux & Iltis 1992), with an update (Pouilly et al. 2014); an insight into the effects of climate change on the ecological functioning of Lake Titicaca using satellite remote sensing (Nuñez 2018); ecological functioning and comparative future scenarios between Puno and Cohana Bays (Bouhassoun et al. 2018); a survey of the impacts of floating cage trout farming on eutrophication (Salas Pludo & Nuñez-Villaba 2019, Ocola Salazar et al. 2020); an inventory of contaminant sources in the Lake Titicaca basin (Ocola Salazar et al. 2022); and the consequences of the deterioration of Lake Titicaca on the rise of socio-ecological inequalities in the Katari basin (Revilla H. 2021). See the references in the Library section of this webpage. 

1. Unique characteristics of Lake Titicaca – Enfasis on Minor Lake ('Lago Menor')

With a surface area of 8 562 km2 (190 km x 80 km) and a volume of 893 km3, Lake Titicaca is the largest freshwater lake in the South American continent. However, Lagoa dos Patos is the largest brackish lake of this continent (10 140 km2), which extends along the Atlantic coast of the Rio Grande do Sul State, Porto Alegre, in Southern Brazil. 

Lake Titicaca is the highest navigable lake in the world, and one (3.809 m s.n.m.) of the highest Large Lake. There are only 10 Large Lakes higher, yet they are much smaller (570-1,860 km2), and mainly located in Tibet (China). In addition, because Lake Titicaca is tropical (16ºS), it surface water doesn't freeze during winter, which may seem very surprising at such altitud. 

Among the Large Lakes, Lake Titicaca is 23th in size (see Fig.1), and one of the 20 older Large Lakes. Yet, as known presently it is only 9,000-year old. It results from a succession of ancestral lakes: Lake Mataro with 55.000 to 51.000 years AP, Lake Cabana with 50.000 years AP, Lake Balivian with 40.000 years AP, Lake Michín with 30.000 to 20.000 AP, and Lake Tauca with 14.000 to 10.000 years AP (see Fig. 2). 

The Tropical Andes Hotspot, including Lake Titicaca, is the most diverse and endemically diverse hotspot in the world (~48.8%). It contains ~1/6 of all plant life in the world, including 30,000 species of vascular plants, making it the leading hotspot for plant diversity. It has the greatest variety of amphibian, bird, and mammal species, and is second only to Mesoamerica in reptile diversity (Zador et al. 2015).

2. What are the origin, symptoms, and consequences of eutrophication? 

Eutrophication is the gradual increase in phosphorus (P) and nitrogen (N) concentrations in an aging lake. Its productivity or fertility increases naturally as the amount of organic matter that can be broken down into nutrients by the mineralizing action of bacteria increases. This material enters the ecosystem mainly by runoff from the land that carries with it the remains and products of reproduction and death of terrestrial as well as aquatic organisms. Water blooms, or high concentrations of microalgae, often develop on the surface, impeding light penetration and oxygen absorption necessary for underwater life.

Cultural eutrophication occurs when human contamination of the water accelerates the natural aging process by introducing wastewater, detergents, fertilizers and other sources of nutrients into the lake. It has dramatic consequences on resources, fisheries and recreational (tourism), and is a main cause of lake degradation.

However, the level of eutrophication of a lake is not visible to the naked eye. It only becomes noticeable when blooms emerge in a final phase. As this phenomenon develops gradually and invisibly, it surprises everyone when it is too late to reverse it. Therefore, permanent and frequent monitoring is indispensable. This is what was lacking during the 2015 rainy season to anticipate the bloom that invaded the northern and central regions of Lago Menor and caused massive mortalities of fishes, frogs, an aquatic birds. 

Eutrophication is generally considered undesirable because its effects significantly impair the ecological and biogeochemical functioning of a lake, as well as interfere with the uses of water and biological resources, such as drinking water supply, irrigation, recreational uses, tourism, fishing, and fish farming. Eutrophication is a natural phenomenon of water enrichment and progressive clogging of water bodies that takes thousands of years, due to the deposition of dead organisms and water matter, as well as sediment inputs by the basin. The demographic growth, the increase of human activities, urbanization, and industrialization, speed up this process in only a few decades, as it has been seen for the impact of the Katari basin on the Bolivian littoral of the Lago Menor in less than four decades.

Eutrophication is materialized by an increase in the concentration of chlorophyll-a (Chl-a, the main photosynthetic pigment of plants) which serves as a 'proxy' (bioindicator) to characterize the trophic status of lakes, from oligotrophic (low productivity), mesotrophic (moderate), eutrophic (high) to hypertrophic (very high) (Thienemann, 1918; Naumann, 1919). These terms indicate the nutrient status, or describe the effects of nutrients on water quality and/or trophic conditions of the water body. They have been linked to specific limit values for certain water quality parameters. As an example, the OECD (1982) International Cooperative Program for the Control of Inland Waters, the Organization for Economic Co-operation and Development, provides specific limit values for total phosphorus (TP), total nitrogen (TN), chlorophyll-a (Chl-a) and Secchi disk disappearance depth (Zs) (Tables 1, 2).

3. Are the surface waters of Lake Titicaca warming rapidly?

There is no specific study analyzing the warming of Lake Titicaca waters over the last decades. However, as an approximation we can use the meta-analysis of O'Reilly et al. (2015) who conducted the most comprehensive study in order to better understand and predict global trends in lake warming among regions of the world. They chose lakes for which there were ≥ 13 years of data. It resulted in 118 lakes sampled in situ, 128 lakes sampled by satellite, and 11 lakes sampled by both in situ and satellite methods. They used the Sharma et al. (2015) database of 154 lakes from North America, Europe, the Middle East, Asia, Africa, and Oceania between 1985 and 2009 (see Fig. 3).

This database, including satellite-assessed Lake Titicaca, incorporates summer lake surface water temperatures (abbreviated LSSWT) with corresponding climatic variables (air temperatures, radiation and cloudiness) and influential geomorphometric features (i.e., latitude, longitude, elevation, lake surface, maximum and mean depth, and volume). Sharma et al. (2015) collected water surface temperatures obtained by the AVHRR (Advanced Very High Resolution Radiometer) satellite, with a spatial resolution of 4 km. For each lake and each day, they extracted a single pixel from manually selected coordinates over each lake, maximizing the distance from any shoreline and island. This avoided possible bias due to contamination from mixed pixels containing both land and water. They only used nighttime data, between 01:00 and 04:00. This ensures that the lake surface temperature remains constant and is not affected by diurnal warming. According to information from O'Reilly et al. (2015), South American lakes show variable warming.

From 23 years of satellite measurements (p = 0.01), Lake Titicaca would have a SSWT warming trend of 0.15 °C/decade. Most lakes are warming and there is great spatial heterogeneity in the trends (Fig. 3). However, 10% of the lakes exhibit cooling trends, although only one of these was significant (p <0.1). The warming trend attained +0.39 ºC/decade as mean, +0.40 ºC/decade as median, and 0.02 ºC/decade as standard error (n = 246). Lake Titicaca belongs to group E, characterized by an air warming of 0.27 ºC/decade, a warm winter, decreasing trends of summer air temperature, and also reduction of cloudiness throughout the year (n = 32): SSWT trend = 0.27 ± 0.31 ºC/decade; Summer air temperature trend = 0.09 ± 0.17 ºC/decade (see Fig. 4). 

Figure 4 - Groups of lakes sharing similar factors influencing SSWT trends are not grouped by region. Lakes that are warming at similar rates due to shared climatic and geomorphic characteristics are widely distributed around the world. Summer air warming trends (°C/decade) by lake groups: A = 0.72; B = 0.39; C = 0.55; D = 0.36; E = 0.27; F = 0.12; G = 0.26; H = 0.53. Source: O'Reilly et al. (2015).

4. Could global warming reinforce the symptoms of eutrophication?

In lakes, climate change intensifies the eutrophication symptoms (Jeppesen et al. 2010; Moss et al. 2011; Fig. 5), and perhaps eutrophication could concomitantly favor climate change (Moss et al. 2011; Fig. 6).

Global warming causes: a) an increase in physiological processes such as reproduction of small forage fish (e.g. Orestias spp. in Lake Titicaca), which, in turn, reduces the impact of piscivorous fish, their predators (trout and silversides, introduced exotic species, very few being free-living in Lake Titicaca); b) a competitive advantage of cyanobacteria over micro-algae because they have an optimal growth at higher temperatures; c) a higher rate of mineralization of organic matter resulting in higher nutrient availability; changes in precipitation, both of which d) lead to higher nutrient inputs; e) increased growth rates and higher survival of aquatic macrophytes. Consequently (Moss et al. 2011; cf. Fig. 5), it generates: f) a higher biomass of microalgae with a higher proportion of cyanobacteria, due to: g) a reduction in grazing of herbivorous zooplankton caused by increased predation by forage fish on zooplankton; h) as a consequence of competition for nutrients and light favorable to cyanobacteria and microalgae, a reduction in submerged macrophytes (such as Chara sp. and Potamogeton sp. in Lake Titicaca) favoring floating macrophytes (such as Lemna and Azola).

Although there is little evidence, eutrophication, conversely, could favor climate change. Eutrophication, through increased photosynthesis, may promote increased carbon dioxide (CO2) fixation. This leads to increased production and respiration, more methane (CH4) release from deoxygenated waters and sediments, and more nitrous oxide (N2O) through denitrification. Both CH4 and N2O are more efficient greenhouse gases (x21 and x310, respectively) than CO2. However, the overall balance between the release of these gases and heat retention due to eutrophication is not known (Moss et al. 2011; Fig. 6). Elucidating the relevance of this mechanism requires further research (Borges et al. 2022).

5. Impact of global warming on the most vulnerable areas of Lake Titicaca

Bradley et al. (2004) analyzed projections of monthly mean temperatures and altitudes from seven coupled atmosphere-ocean general circulation models along the Cordilleras between North and South America. At all latitudes, projected temperature changes increase with elevation. In the Southern Hemisphere, temperature increases of >2.5°C are predicted in the mountainous zone from 10°S (in Peru) through Bolivia to 40°S (in Chile/Argentina). They considered the period 2001-2020 as the "present time" and 2061-2080 as the "future". They estimated that by 2070 the atmospheric CO2 concentration would reach 560 ppm, i.e. double the pre-industrial era. In the most pessimistic case (RCP8.5 scenario), they predicted+2°C to +4°C by mid-century for the Altiplano. This seems a lot considering how much the temperature has increased in the last 60-70 years.

According to Bradley et al. (2004; Fig. 7), by the 2061-2080 horizon, Lake Titicaca and the Altiplano will suffer +2.25°C of warming compared to present time. This increase would be lethal for most animal and plant species that already coexist at the limit of their physiological capacities. Many are already endangered or threatened with extinction. This +2.25ºC increase is well above the +1.5ºC warming that should not be exceeded, according to the Paris Climate Agreement at COP 21 in 2015, because beyond that we enter the unknown.  

It is well documented that shallow lakes obey the principles of dynamic models where strong perturbations are able to initiate the shift between alternative equilibrium states: i.e. 'clear waters' (with little phytoplankton) dominated by aquatic macrophytes (plants) vs 'turbid waters' dominated by phytoplankton, with few macrophytes (Scheffer et al. 1993).

Based on the results of a 370,000 year paleoecological record (a bottom sediment core) from Lake Titicaca, Bush et al. (2010) envision an even more dramatic scenario than Bradley et al.'s (2004). They proposed a conceptual model with a positive feedback mechanism that promotes desiccation until much of the lake basin can be reduced to swamps. The authors proposed that the usual concept of plant species migrating to higher elevations with warming would not be applicable in the Altiplano (Fig. 8-Left). They suggest that a tipping point could exist above +1-2°C from current temperatures, where the relatively benign agricultural conditions of the northern Altiplano would be replaced by arid and inhospitable climates. The positive feedback mechanism would be: the increase in temperature would initiate a reduction in precipitation, causing a lowering of the lake level, which (being shallow) would cause a significant reduction in the surface area of the water mirror, and thus less moisture and more evaporation, accelerating the lowering of the level, and so on (Fig. 8-Right).

6. Lake Titicaca level dropping since the last two decades 

Since 1973, the Lake Titicaca level has fluctuated between a maximum of 3,811.28 m a.s.l. (April 1986) and an extraordinary minimum of 3,807.49 m (December 1998). Meanwhile, in the last 100 years, the minimum historical level observed in Puno was 3,806.23 m in 1944. Flood (3,810.50 m) and drought (3,807.80 m) alert levels are defined when the competent authorities are informed. In 2003, the level was closed to the flood alert level, and dropped since then down to close to the drought level presently. The highest levels occur in April-May and the lowest in December. April-May 2023 levels are significantly lower than in previous years. On July 18, 2023, 3,807.78 m was recorded (i.e., 2 cm below the drought alert level). Therefore, in the most unfavorable case, a new historical minimum level of 3,807.16 m could be reached in December 2023 (i.e., 64 cm below the drought alert level and 33 cm below the historical minimum level of 1998), depending on the pluviometric regime in the tributary basins (SNHN 24/07/2023, see Fig. 9).

A period of prolonged drought, such as the current one (2023) aggravated by an intense El Niño phenomenon predicted to last until 2025, could prevent the connection of Lago Menor to the Desaguadero River. Consequently, it would harm the water supply of Lake Urú Urú, the city of Oruro, the irrigation systems, and finally Lake Poopó. Although Oruro is supplied by groundwater, there must be a connection between the river and the aquifers that may hinder recharge due to the reduction of the Desaguadero's flow. The ALT (autonomous binational Authority of Lake Titicaca) has already sent a warning report. For now the floodgates of the regulation dam on the Desaguadero river outlet (to the south of Lago Menor) are open. Yet, according to the operation protocol, when reaching 3,807.35 m a.s.l., a maximum regulation must be executed, leaving only a 2 m3/s outflow.

Most of the Bolivian sector of Lago Menor is less than 5 m deep. The map in Fig. 10 reveals the dramatic consequences of a 4 m drop in the water level of Lago Menor. In particular, it could result in the separation of the deeper northern region including the Chuá trench (40 m) from the central and southern regions (at the level of the islands), which would progressively dry up, disconnecting Lago Menor from the Desaguadero river which would dry up. 

7. Most research on 'Lago Mayor' and Puno Bay vs few studies on the vulnerable 'Lago Menor' and Cohana Bay 

Because of its vastness, Lake Titicaca (area 8,200 km2, 190 km from northwest to southeast, volume 893 km3) belongs to the Large Lakes (≥ 500 km2) the World and is the largest freshwater lake in South America. This fascination for its dimensions, in particular its maximum depth (> 285 m), made 'Lago Mayor' always the center of studies attention (see Fig. 11), since the first expeditions of famous naturalists, such as D'Orbigny (1826-1833)[http://www.memoriachilena.gob.cl/602/w3-article-9529.html], Agassis (1876) [https://en.wikipedia.org/wiki/Louis_Agassiz], Neveu-Lemaire (1906) [https://es.wikipedia.org/wiki/Maurice_Neveu-Lemaire] and the Percy-Sladen-Trust Expedition led by Gilson  (1937) [https://www.barterbooks.co.uk/catalog/product_info.php?products_id=208241&osCsid=bkst9jfh4knqdba6o2ojd2rjg3]. In the second half of the 20th century, limnology focused on understanding the functioning of the World's Large Lakes, in particular with the International Man and the Biosphere Program (MAB) launched in 1972 by UNESCO (Dyer & Holland 1988). Its main objective was to establish a scientific basis for a better relationship between humans and the environment.

Richerson et al. (1977) conducted the first functional limnology study of Titicaca 'Lago Mayor', focusing on the annual cycle of phytoplankton, primary production, zooplankton, and heat balance, based on its monomictic character (only one vertical mixing per year). They monitored twice a month throughout 1973 seven stations in its deeper northern part. They published these data about ten years later along with data from a monthly monitoring conducted for two years (1981-1982) at two deep stations, one near the coast (W) and one further inland (Z) Richerson et al. (1986) (see Fig. 12). This work was the fruit of a collaboration between the University of California and IMARPE. With their book, Northcote et al. (1991) stimulated important research on the pollution and eutrophication of Bay of Puno, due to sewage discharges from Puno and Juliaca cities, and its shallow depth. Its deterioration increased because Puno lacked adequate treatment due to the collapse of the only Espinar wastewater treatment plant (WWTP).

Lazzaro (1981) conducted the first limnological study of 'Lago Menor', analyzing the annual cycle of physical-chemical characteristics, phytoplankton and primary production, with a frequency of 18 days (Landsat-2 satellite pass), at 8 stations in both the Bolivian and Peruvian sectors. Since at this time the rivers did not discharge polluted wastewater in the littoral zone, these representative stations were located in the pelagic zone. This study revealed their oligotrophic (i.e., nutrient-limited) and transparent, but polymictic (daily mixing by thermal winds) characteristics. Today, this research represents the baseline of the characteristics of 'Lago Menor' before it was impacted by climate change, combined with the effects of human activities amplified by rapid population growth. At that time, the small coastal towns were not electrified; the city of El Alto did not exist (only La Ceja around the airport); Viacha was a small town; plastic packaging did not exist; chemical fertilizers and agrochemicals were not used; agriculture was not mechanized; sailboats and totora reed rafts predominated; outboard motorboats were scarce; domestic and industrial pollution to the lake did not exist; drinking and cooking with lake water was possible; there was no domestic nor industrial pollution from the urban suburbs of El Alto-Viacha; and there was no intensive agricultural waste. In their book, Dejoux & Iltis (1992) synthesized the knowledge about Lake Titicaca corresponding to the period 1970-1990, while Lazzaro & Gamarra (2014) presented a synthesis on the evolution of the ecological and photobiological conditions of Lake Titicaca, based on the dispersed available literature, in the book edited by Pouilly et al. (2014).

8. The binational yearly campaigns on a network of limnological stations on the overall lake

Lake Titicaca has unique characteristics, being both tropical and at high altitude, and suffering from the combination of intense climate change and accelerated anthropization. Paradoxically, prior to the start of this OLT observatory pilot project in 2019, Lake Titicaca was the only Large Lake not to have permanent monitoring of its water quality, nor of its microalgae blooms. Only since 2014 have there been two annual binational expedition programs: one on water resources and water quality conducted by ANA (Autoridad Nacional del Agua, through AAA - Autoridad Administrativa del Agua, in Puno), and another on fish biomass (ECERP) conducted by IMARPE and PELT, both coordinated by ALT. Bolivian institutions (MMAyA, UOB, IPD-PACU, UMSA) did not always participate effectively (see Fig. 14). Both campaign programs were implemented over more than 100 limnological stations and lasted about 1 month, along transects from the Puno bay in 'Lago Mayor' to the Desaguadero river outlet in 'Lago Menor' (see Fig. 15). The last water quality campaign was performed in 2019, and the last biomass campaign in 2021. 

The original campaign design has at least two drawbacks: (a) As the sampling of Lago Menor is done about one month later than the sampling of Lago Mayor, the limnological conditions of the two lakes may have been influenced not only by their distinct morphometry, but also by differences in meteorological conditions that may have occured. (b) As the overall sampling is performed by the two Peruvian vessels, which can't navigate in water depths less than two meters, they can't explore the littoral and shallow regions of lago Menor, thus underestimating the contaminated and eutrophicated areas. To eliminate these limitations, I convinced the organizers that the November 2015 and August 2016 campaigns will last no more than 15 days, during which the two Peruvian vessels will survey Lago Mayor, meanwhile our INTI boat will survey Lago Menor. This is what I did with my team of students and associated researchers of the Institute of Ecology (IE) of the Universidad Mayor de San Andrés (UMSA). This way we sampled (physico-chemistry, phytoplankton, zooplankton) and measured the biogeochemistry with multiparametric probes (HydroLab DS5, FluoroProbe BBE) and the attenuation of the visible and UV radiations in the water column  with a spectroradiometer (Biospherical C-OPS), at 65 and 85 stations, respectively, covering the Bolivian and Periuvian sectors of Lago Menor. Unfotunately, for the subsequent campaigns, the previous sampling design has been taken over. Anyway, the highly time-consuming analyses of the samples and the data that took mostly three months, plus the overall elevated financial cost,  make us convinced that: (a) Performing such sampling campaigns once or even twice a year did not allow us to make any assessment of the ecosystem's evolution, nor any forecast, even in the short term. (b) Thus, a high-frequency automatic monitoring based on an autonomous solar-driven platform (buoy) to measure simultaneously the weather and the in situ conditions over the whole water column (profiling) was THE appropriate solution for the future. (c) Gathering all the generated databases within a permanent virtual envrionmental observatory (GeoVisor, webpage) shareable with users (populations, scientists, managers) was indispensable to improve our knowledge on the ecological functioning of Lake Titicaca, and prevent adverse effects, such as eutrophication and blooms. Thus, the leading idea of the OLT observatory was born, later it has been financed by the PNUD 05-B-05 Pilot Project.

Figure 14 - The scientific research fleet in Peru: The BIC PELT (dedicated to water quality; on the left) and the BIC IMARPE VIII (dedicated to fishery resources; at center), both State vessels are 15 m long and about 2 m draft, which prevents them from studying the littoral zones of Lago Menor, operate mainly in Lago Mayor. In Bolivia: the INTI boat of Don Máximo Catari Cahuaya, in Huatajata (on the right), 10 m long and about 0.5 m draft, rented by the OLT observatory team for all their campaigns, particularly suitable for investigating the shallow areas of Lago Menor.

9. Eutrophication of the Bolivian coastline of Lago Menor mainly from the uncontrolled urban contamination of El Alto 

Desde los años 1970', la bahía interior de Puno sufre de blooms fitoplanctonicos de manera recurrente por la ubicación de la ciudad de Puno a la orilla del lago, el colapso de Espinar, su PTAR subdimensionada y colapsada, sin tener el beneficio de la filtración natural de las descargas de nutrientes y materia organica por la ausencia de un cordon litoral de totorales (macrofitas emergentes). En contraste, parece que los abundantes totorales del litoral del Lago Menor, en particular los densos totorales de la bahía de Cohana impidieron la occurrencia de blooms por varias decadas, a pesar de las masivas descargas de aguas residuales provenientes de la urbanización de El Alto-Viacha por la cuenta Katari hasta las bahías de Cohana (región central del Lago Menor) y de Cumana (región norte del Lago Menor), ademas de las descargas por el río de Batallas hasta el Sur de la isla de Cojata (frente a Huarina), en la región noreste. The Katari watershed that discharges wastewater from El Alto-Viacha into Cohana bay, only relies on the two WWTPs of Puchukollo and Laja, which are undersized, not fully connected to the sewer system. 

Since the 1970s, the inner bay of Puno has suffered from recurrent phytoplankton blooms due to the location of the city of Puno on the shore of the lake, the collapse of Espinar, its undersized and collapsed WWTP, without benefiting of natural filtration of nutrient and organic matter discharges due to the absence of a littoral cordon of Totora (i.e .endemic cattails, emergent macrophytes). In contrast, it appears that the abundant 'totorales' along the shoreline of Lago Menor, in particular the dense 'totorales' of Cohana Bay, prevented the occurrence of blooms for several decades, despite massive sewage discharges from the El Alto-Viacha urbanization through the Katari watershed to the bays of Cohana (central region of Lago Menor) and Cumana (northern region of Lago Menor), as well as discharges through the Batallas river to the south of Cojata island (in front of Huarina), in the northeastern region...

... Until, in April-May 2015 appeared the first ever documented phytoplankton bloom that extended in the northern and central regions of Lago Menor. This has been a complete surprise and incomprehention by the coastal residents who didn't know what produced this extensive surface green soup. It resulted that an unicellular green microalga 10-µm in diameter, Carteria sp., was the responsible. The later decomposition of this bloom resulted in massive mortalities of fish, frogs, and even waterfowl (see Fig. 16). 

The study site of the OLT observatory was defined including the northeast region (from the Cojata island to the Cumana bay) and central region (Cohana bay towards Suriqui, Pariti and Sicuya islands, and Taraco peninsula) based on the extension of the 2015 phytoplankton bloom as a consequence of the major point multiple contamination (domestic, industrial, mining) originating from the Katari watershed (see Fig. 18). Lanza et al. (2024) demonstrated the beneficial performance of totora patches (native emergent aquatic macrophyte, Schoenoplectus californicus) in shallow areas (<< 1m) of Cohana Bay in purifying nutrients discharged from the mouth of the Katari River, as illustrated by a decreasing gradient of eutrophication towards the bay outlet, opposite Suriqui Island. This finding confirms the importance of preserving the totora coastline, and its potential in phytoremediation, as an ecological engineering tool (i.e. a nature-based solution), for cost-effective control of lake eutrophication, complementing the (compact) wastewater treatment plants that will have to be urgently deployed on the rivers in the Katari watershed anyway. 

Ventusky© - live weather

Ventusky web is a software of Cheka Weather Company. It allows to observe weather conditions in real time, also in the past and one week in advance. The weather data providers are DWD and NOAA. The modeled variables are: precipitation, clouds, wind speed/direction, atmospheric pressure, thunderstorms, humidity, waves, snow cover, air quality, among others.

Double clicking on the image will take you to the visualization of the lake with the program on the web: https://www.ventusky.com/ , where you can select the date, time, and variable of interest.

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