Modelling nutrient loads and eutrophication assessment of lake Yahuarcocha : master thesis

Pullas Guarderas, Nathan Andrés (author), Atanasova, Nataša (mentor), Krzyk, Mario (comentor), Pacini, Nicola (comentor)

Although significant rehabilitation efforts have been carried out in the past to enhance the ecological and chemical status of Lake Yahuarcocha, it continues to experience considerable pressure from its surrounding environment. In this master's thesis, we examined and modeled the origins of nutrient loads from the contributing areas as well as the sources that directly impact the lake. To achieve this, we developed a model to estimate nutrient loadings from the watershed. Following the Kirchner-Dillon formulation, the model was used to predict the mean phosphorus concentration ([P]) based on the balance between external loading and hydraulic characteristics. We considered phosphorus to be the sole limiting factor affecting the quality of the lake. In our analysis we considered point and dispersed pollution sources. The model was calibrated by refining the Phosphorus Export Coefficients for various land use categories to better reflect the specific conditions of the Yahuarcocha micro-basin. Initially, these coefficients were based on general values from literature, but they were adjusted during the calibration process to bring the predicted lake concentration within an acceptable <20% difference of the observed monitoring data. The calibrated model identified surface runoff as the largest source of phosphorus loading, accounting for almost 70% of the total load. This is primarily a result of agricultural activities within the watershed. The model also highlighted that anthropogenic inputs and runoff enhance the lake's internal nutrient load, a critical factor that significantly contributes to algal blooms. To achieve a mesotrophic state (target 20 μg P/L), the allowable total phosphorus (TP) load for the lake is estimated to be ≈ 795 kg P per year. The current total P load of 5,301 kg P per year overpasses this allowable load by approximately 7.65 times. In response to these findings, we propose a multi-faceted set of recommendations. These measures are designed to not only reduce nutrient loads at their source but also foster a more sustainable development of the tourism-dependent community.

• Language: English
• Keywords: master thesis, eutrophication, Vollenweider, phosphorus loading, massbalance, surface run-off, nonpoint source pollution, anthropogenic activity, best management practices (BPMs), 4r nutrient management, circular economy, wastewater treatment, constructed wetlands, phosphorus cycle
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [N. A. Pullas Guarderas]
• Year: 2026
• Number of pages: 1 spletni vir (1 datoteka PDF (X, 29 str.))
• PID: 20.500.12556/RUL-183663
• UDC: 556.5(866)(043.2)
• COBISS.SI-ID: 282077955
• Publication date in RUL: 17.06.2026

Secondary language

• Language: Slovenian
• Title: Modeliranje obremenitev s hranili in ocena evtrofikacije jezera Yahuarcocha

Abstract

Kljub precejšnjim prizadevanjem za sanacijo, ki so bila izvedena v preteklosti z namenom izboljšanja ekološkega in kemijskega stanja jezera Yahuarcocha, to še naprej doživlja velik pritisk iz okolice. V tem magistrskem delu smo proučili in modelirali izvor obremenitev s hranili iz prispevnih območij ter vire, ki neposredno vplivajo na jezero. V ta namen smo razvili model za oceno obremenitev s hranili iz povodja. Z uporabo Kirchner-Dillonove formulacije je bil model uporabljen za napovedovanje povprečne koncentracije fosforja ([P]) na podlagi ravnovesja med zunanjo obremenitvijo in hidravličnimi značilnostmi. Fosfor smo obravnavali kot edini omejujoči dejavnik, ki vpliva na kakovost jezera. V analizo smo vključili točkovne in razpršene vire onesnaževanja. Model je bil umerjen z izpopolnjevanjem koeficientov izvoza fosforja za različne kategorije rabe zemljišč, da bi bolje odražal specifične razmere v mikro-povodju Yahuarcocha. Prvotno so ti koeficienti temeljili na splošnih vrednostih iz literature, vendar so bili med postopkom umerjanja prilagojeni tako, da so predvideno koncentracijo v jezeru približali opazovanim podatkom spremljanja na sprejemljivo razliko pod 20 %. Umerjeni model je površinski odtok prepoznal kot največji vir obremenitve s fosforjem, ki predstavlja skoraj 70 % celotne obremenitve. To je predvsem posledica kmetijskih dejavnosti v povodju. Model je izpostavil tudi, da antropogeni vnosi in odtok povečujejo notranjo obremenitev jezera s hranili, kar je ključen dejavnik, ki pomembno prispeva k cvetenju alg. Za dosego mezotrofnega stanja (ciljna vrednost 20 μg P/L) je dopustna obremenitev jezera s skupnim fosforjem (TP) ocenjena na ≈ 795 kg P na leto. Trenutna skupna obremenitev s fosforjem, ki znaša 5.301 kg P na leto, presega to dopustno obremenitev za približno 7,65-krat. Kot odgovor na te ugotovitve predlagamo nabor večplastnih priporočil. Ti ukrepi so zasnovani tako, da ne le zmanjšajo obremenitve s hranili pri viru, temveč tudi spodbujajo bolj trajnosten razvoj skupnosti, ki je odvisna od turizma.

• Keywords: magistrska dela, evtrofikacija, obremenitev s fosforjem, masna bilanca, površinski odtok, razpršeni viri onesnaževanja, antropogena dejavnost, najboljše prakse upravljanja (BPMs), 4R upravljanje s hranili, krožno gospodarstvo, čiščenje odpadnih voda, rastlinske čistilne naprave, krog fosforja