Application of a Three-Dimensional Water Quality Model as a Decision Support Tool for the Management of Land-Use Changes in the Catchment of an Oligotrophic Lake

Abstract

While expansion of agricultural land area and intensification of agricultural practices through irrigation and fertilizer use can bring many benefits to communities, intensifying land use also causes more contaminants, such as nutrients and pesticides, to enter rivers, lakes, and groundwater. For lakes such as Benmore in the Waitaki catchment, South Island, New Zealand, an area which is currently undergoing agricultural intensification, this could potentially lead to marked degradation of water clarity as well as effects on ecological, recreational, commercial, and tourism values. We undertook a modeling study to demonstrate science-based options for consideration of agricultural intensification in the catchment of Lake Benmore. Based on model simulations of a range of potential future nutrient loadings, it is clear that different areas within Lake Benmore may respond differently to increased nutrient loadings. A western arm (Ahuriri) could be most severely affected by land-use changes and associated increases in nutrient loadings. Lake-wide annual averages of an eutrophication indicator, the trophic level index (TLI) were derived from simulated chlorophyll a, total nitrogen, and total phosphorus concentrations. Results suggest that the lake will shift from oligotrophic (TLI = 2-3) to eutrophic (TLI = 4-5) as external loadings are increased eightfold over current baseline loads, corresponding to the potential land-use intensification in the catchment. This study provides a basis for use of model results in a decision-making process by outlining the environmental consequences of a series of land-use management options, and quantifying nutrient load limits needed to achieve defined trophic state objectives.

Lake Restoration in New Zealand

“…Irrigation is linked to increased intensity of pastoral land use (i.e., increases in stock density and fertiliser use) and has been implicated in increased trophic status of some of the most oligotrophic lakes in New Zealand (Trolle et al . ). The potential for synergistic effects of climate change and land‐use intensity on lake eutrophication (Hamilton et al .…”

“…Agricultural production is likely to remain a major economic driver of the New Zealand economy for the foreseeable future and irrigation of dryland areas is expanding rapidly, with New Zealand having the highest rate of increase in irrigated agricultural land areas of any country in the Organisation for Economic Co-operation and Development (OECD). Irrigation is linked to increased intensity of pastoral land use (i.e., increases in stock density and fertiliser use) and has been implicated in increased trophic status of some of the most oligotrophic lakes in New Zealand (Trolle et al 2014). The potential for synergistic effects of climate change and land-use intensity on lake eutrophication (Hamilton et al 2013) suggests that mitigation for these effects may need to be increased beyond current restoration targets.…”

Acercamiento a los procesos de modelación de la calidad del agua en una subcuenca. Caso del río Virilla, Costa Rica

“…Actualmente las técnicas de modelación o simulación matemática de la calidad del agua, son herramientas muy importantes y ampliamente utilizadas en el nivel mundial, en el manejo integrado del recurso hídrico, una de las razones primordiales es que, a diferencia de los sistemas de monitoreo convencionales, los modelos matemáticos pueden brindar mayor cantidad de información en tiempo y espacio (Benedini y Tsakiris, 2013). Otro aspecto importante es que mediante la modelación se pueden reproducir una serie de eventos, con el propósito de evaluar escenarios derivados de las medidas de manejo implementadas dentro de los límites de la cuenca a estudiar (Nguyen, Keupers y Willems, 2018;Trolle et al, 2014).…”

Seasonal Succession of Phytoplankton Functional Groups and Driving Factors of Cyanobacterial Blooms in a Subtropical Reservoir in South China

“…There are many methods for assessing the nutritional status of aquatic environments. The assessment of eutrophication in aquatic ecosystems is essentially a multivariate comprehensive decision-making process for aquatic ecosystems [21][22][23]. Based on the EU Water Framework Directive [19], Padisák et al developed the Q index method, based on the taxonomy of the phytoplankton functional groups, to evaluate the ecological status of different types of water bodies [24].…”