Organización de datos de irradiancia solar

This research has employed the Soil and Water Assessment Tool (SWAT) and remote sensing techniques to address the research objectives. This study has shown which land use activities contribute to water quality and quantity problems of the catchment and has also identified the trends in land use and climate change implications for water resources. A framework of land use change patterns and future scenarios has also been developed to guide land use change policy decisions that could deliver improved environmental outcomes.

The study has critically assessed and identified the spatial distribution of pollution sources in the catchment through modeling and mapping to achieve the first objective. It was found that some areas are contributing more nitrogen (N), phosphorus (P) and sediments than others. The distributions show that some sub-basins in the catchment yield as much as 25.5kg N/ha, 2.89kg P/ha and 8.4tonnes sediment/ha per year respectively. Similarly, the catchment hydrologic component is found to be unevenly distributed. For instance, the western part of the catchment receives more

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rainfall than other parts. Other hydrologic parameters/processes such as evapotranspiration (ET) and surface runoff are unevenly distributed. These analyses and findings were covered in chapter five.

In order to achieve objective two, nutrient/pollutant fluxes from the various land use types were analysed and quantified using the SWAT model. The analyses (presented in chapter five) indicate that pastoral land use, vineyards, gorse and broom, and native forests occupied the largest areas of the catchment. The four land use categories also constitute the largest contributors in terms of N, P and sediment yield in the catchment.

Remote sensing techniques were also utilised to analyse the rate of land use change and projected the probable state of land use coverage into the near future (year 2030), assuming the existing trends continue. The land use change analyses indicate that while the majority of the land use types in the catchment will decrease in area coverage, beef/dairy and vineyards are expected to expand. Beef/dairy land use will grow by 1.8% in 2020, 7.3% in 2025 and 13.0% in 2030 while vineyards are expected to increase by 2.2%, 9.3%, and 13.5% for the 2020, 2025 and 2030.

Further analyses were carried out to determine the rate or trend of pollutant yields from both present and future land use coverage in the catchment to meet the third objective. These were presented in chapter six, and show that the rate of N, P, and sediment yields in the catchment will increase progressively in the future.

The sustainability of the projected expansion in land use types, especially dairy land use, in relation to the availability of water to drive the growing dairy sector, was also assessed. Sourcing water externally from outside the catchment (e.g. via the Hurunui Water Project) offered a window of opportunity for keeping up with the possible increase in water demand for the increasing dairy sector of the catchment since dairying cannot thrive without water.

Research objectives four and five were designed to establish the relationship between future land use change and pollution discharge on surface flow as well as estimate the impacts of climate change on surface flow and water quality. Current trends in atmospheric temperature warming, and also by analysis of how various land use change scenarios could help in reducing nutrients (N and P) yield under different climate scenarios is covered in chapter seven. It was found that systematic seasonal and annual changes in temperature and precipitation over the catchment are expected under the three Representative Concentration Pathways (RCP 4.5, 6.0, 8.0). Substantial reductions in rainfall especially during winter seasons are expected while summer is expected to experience slight

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increases in rainfall. Irregularities in rainfall and temperature patterns are expected to cause fluctuations in surface flow, and likewise in groundwater levels over summer, autumn, winter and spring, as well as on annual basis.

The impact of land use change on nutrient yield in the Waipara catchment is found to be influenced mainly by two climate change conditions (RCP 4.5 and RCP 6.0). All four land use change scenarios (sheep and beef to forest; beef and dairy to forest; beef and dairy to vineyards; sheep and beef to vineyards) exhibited notablereductions in nitrogen (N) and phosphorus (P) yields under climate change scenarios RCP 4.5 and 6.0.

SWAT has been used worldwide for the study of both large and small catchment hydrology and land use impact applications. However, little research has been carried out using SWAT in examining the impact of land use on water quality in this part of the world. The few New Zealand based SWAT applications are limited in scope to river catchment hydrology and nutrients/contaminants simulations (Ekanayake and Davie, 2005; Cao et al., 2009; Morcom, 2013; LERNZ, 2015; Me et al. 2015; 2017). While the application of SWAT in New Zealand is not new, its use in assessing the combined land use and climate change impacts on water resources in the current study is. Employing GCMs and SWAT in this thesis to simulate the impacts of future climate scenarios and land use change scenarios is the first such study in New Zealand.