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Item Using rainwater tanks as stormwater control measures to improve runoff and water quality management in urban areas : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Water Resource Management at Lincoln University(Lincoln University, 2020) Odeh, MohamadUrbanisation and associated human activities impact rivers and streams that flow through urban areas. Impacts include receiving large volumes of stormwater runoff loaded with high concentrations of contaminants during rainfall events. Different decentralised stormwater control measures such as raingardens and rainwater harvesting tanks have been used to mitigate stormwater runoff in urban areas, and different natural materials such as mussel shell waste have been incorporated in these measures to remove contaminants in runoff near pollution sources. Rainwater tanks have been recently recognised as stormwater control measures based on the tank’s ability to detain roof runoff during rainfall events. Despite the increased attention on using rainwater tanks to mitigate stormwater runoff in urban areas, there is still a lack of knowledge regarding their effectiveness to mitigate stormwater runoff at different scales of urban areas such as industrial and residential lands. Furthermore, the use of filtration units in the rainwater tanks to improve the mitigation performance and to remove common contaminants in roof runoff such as zinc have not been investigated yet. The mussel shell wastes have been used to remove dissolved zinc from stormwater runoff in stormwater control measures. However, the removal efficiency of zinc during different filtration conditions such as varied flow rates and short contact times with water have not been fully investigated yet. Therefore, this thesis investigated the use of mussel shell waste as filtration media in rainwater tanks to remove zinc from roof runoff, and evaluated the use of rainwater tanks to mitigate stormwater runoff at residential and industrial scales in Christchurch, New Zealand. The effectiveness of mussel shell to remove zinc was investigated for untreated mussel shell (UTMS), and heat-treated mussel shell (TMS). Two types of filtration units were designed to investigate the use of UTMS and TMS as filtration media in the rainwater tank. The first filtration units included 1.0 m depths of the filtration media connected to a gravity-driven outlet, and the second filtration units included 0.8 m depths of the filtration media connected to a siphonic-driven outlet. An actual roof runoff was collected from galvanised roofing, and the removal performance of zinc was estimated during controlled saturated flow rates of 1, 3, 5, 10 L/min. The collected roof runoff showed high concentrations of dissolved zinc with an average zinc concentration of 3347.2 μg/L, which is ca. 200 times higher than the recommended concentration of zinc in urban streams (i.e. 15 μg/L) to protect 90% of the freshwater organisms according to the ANZECC’s guidelines (ANZECC, 2000). Both the TMS and UTMS demonstrated high removal efficiencies of dissolved zinc. The heat treatment of the mussel shell generally improved the removal performance of dissolved zinc. The TMS media showed significantly higher (p ≤0.05) removal performance of zinc compared to the UTMS media for the tested flow rates during 0.8 m depths of filtration media, while the TMS showed higher average removal efficiencies but with there was no significant difference (p > 0.05) for the tested flow rates during the 1.0 depths. For all flow rates, the overall average removal efficiencies of the TMS were estimated at 94% and 82% for 1.0 m and 0.8 m depths of filtration media respectively, while the overall average removal efficiencies of the UTMS were estimated at 92% and 72% for 1.0 m and 0.8 m depths of filtration media respectively. The removal performance of zinc decreased as water flow rates through the TMS and UTMS increased. The EPA's Storm Water Management Model (SWMM) was used to evaluate the mitigation performance of rainwater tanks for two urban blocks that represented the residential and industrial land use in Christchurch, New Zealand. Three management scenarios were simulated using 5-min time steps throughout a 12-year period starting from 4 November 2007 until 4 November 2019. The first management scenario represented the Business As Usual ( BAU) conditions, and used as the reference of actual stormwater peaks and total volumes of outflow in the selected blocks. The second management scenario represents using Rainwater Harvesting for Toilet Flushing (RWH-TF) uses which simulated the use of collected rainwater to supply water for toilet flushing uses in the existing buildings of the selected blocks. The third management scenario represents using Rainwater Harvesting for Stormwater Treatment (RWH-ST) uses which simulated the use of rainwater tanks and filtration units as stormwater detention units to collect, and slowly discharge treated roof runoff into the stormwater network. The simulation results showed effective mitigation performance in both the residential and industrial blocks. The average reductions in peak runoff during the RWH-ST scenarios were estimated at 52.9% and 45% in the residential and industrial blocks respectively, while the average reductions in runoff volumes were estimated for 37.3% and 19.5%. The RWH-TF scenarios showed lower peak reductions with averages estimated at 36.3% and 23.9% in the residential and industrial blocks respectively, while the average volume reductions estimated at 42.9% and 27.5% in the residential and industrial blocks respectively. During RWH-ST scenario, the integrated rainwater tanks with filtration units showed effective treatment performance throughout the simulation period with more than 99% and 58% treatment ratio of roof runoff in the simulated residential and industrial blocks respectively. The results of this thesis exposed potential benefits for using integrated rainwater harvesting tanks (i.e. with filtration units) as stormwater control solutions to improve runoff and water quality management in urban areas. In particular, the use of mussel shell waste as filtration media in rainwater tanks provided cost-effective solutions to remove metals from runoff in order to protect the ecological conditions in urban waterways, and the use of rainwater tanks reduced stormwater runoff volumes and peak flows during rainfall events at both residential and industrial scales.Item Assessing impacts of climate change on water resources and agriculture: A case study of Tonle Sap basin, Cambodia : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Water Resource Management at Lincoln University(Lincoln University, 2020) Ly, SoknaCambodia’s Tonle Sap Lake is the largest permanent freshwater body not just in Cambodia, but in Southeast Asia, and is also one of the world’s richest lacustrine-wetland ecosystems. Agriculture and fisheries provide the primary livelihoods of people living in the area. Despite a high abundance of natural resources, the area around Tonle Sap Lake is known to be one of the poorest areas in Cambodia, where most people derive their livelihoods directly from the resources provided by the lake. This study aims to assess the impacts caused by climate change on water resources and agricultural production in the basin by looking into future changes of streamflow of the tributary rivers, flood pulse and the paddy rice areas supported by the Mekong River’s flood pulse. For this study, six climate change scenarios were employed to assess future change in rainfall and river flow. They are the result of the combinations between three global circulation models (GFDL-CM3, GISS-E2-R-CC and IPSL-CM5A-MR) and two representative concentration pathways (RCP4.5 and RCP8.5). HEC-HMS was used for simulating rainfall and runoff for 11 sub-basins that feed the Tonle Sap Lake. HEC-RAS was used for computing inundation areas around the lake. Both models were calibrated and validated using data for the year 2000–2005 and 2006–2007, respectively. The results from HEC-RAS were exported in a format that enabled further analysis in GIS to examine changes to paddy rice areas at both the basin- and sub-basin scales. Both HEC-HMS and HEC-RAS model performances were evaluated using statistical indices NSE and R2. The indices indicated satisfactory performance for both simulation models with NSE > 0.40 and R2 > 0.60 for HEC-HMS and NSE > 0.60 and R2 ≥ 0.90 for HEC-RAS. The main findings in the study were the reduction of annual streamflow that is projected to occur in almost every sub-basin under all climate change scenarios up to the year 2030. The Dauntri sub-basin is projected to experience the highest streamflow decrease, up to 62.53%, while streamflow in the Sen and Boribor sub-basins showed a slight increase. The results from HEC-RAS suggest a decrease of flood pulse extent under all climate change scenarios. The magnitudes of decrease are almost the same for each scenario with an average decrease of around 10%. The Sen sub-basin showed the greatest reduction of flooded areas (13.82%) while Sangker was projected to decrease the least (2.00%). Though the Sen and Boribor catchments show an increase in streamflow, the increase is offset by the reduced flows in the remaining catchments, thus contributing less flow to the lake overall, leading to its reduced area. The results also suggest a decrease in paddy rice areas supported by the flood pulse. Stuang is the sub-basin with the highest reduction of paddy rice areas of up to 28.36%, while Sangker remains the sub-basin with the least reduction (2.67%). Some noteworthy implications arise from the main findings. The decrease of flows in the tributary rivers suggests an increase in drought risk and consequences for household water supply and surface irrigation that divert or extract water from those rivers. The change of the extent of flood pulse suggests that there will be lower nutrients and sediment loads and this would substantially impact the ecosystems in the lake and other connected parts. The reduction of paddy rice areas underscores the potential implications for social and economic development such as food insecurity, unemployment and economic impacts.Item The effects of high lake levels due to climate change on lakeside communities and adjacent land use: Case study: Lake Ellesmere/Te Waihora : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Water Resource Management at Lincoln University(Lincoln University, 2019) Zarour, DaliaThis research aims to assess the effects of sea-level rise on Lake Ellesmere/Te Waihora’s current opening regime and consequently on adjacent land and it’s lakeside communities. The research also aims to assess Lake Ellesmere/Te Waihora’s lakeside communities’ level of preparedness to adapt to these anticipated changes. Unlike other natural hazards that occur abruptly, sea-level rise is incremental and foreseeable, and its effects on coastal areas and communities are expected to occur gradually. Thus, it is crucial to start planning now for future sea-level rise to reduce its adverse impacts on coastal areas and communities. Intermittently closed and open lakes and lagoons (ICOLLs) such as Lake Ellesmere/Te Waihora are vulnerable to the effects of sea-level rise due to their setting within the coastal landscape. The water level of many ICOLLs around the world, including Lake Ellesmere/Te Waihora, are managed by artificially creating a temporary opening through the barrier separating the ICOLL from the sea and inducing premature breakout to protect adjacent land and communities from inundation. The artificial opening is induced when a predefined opening trigger value is reached. The success of the artificial opening is dependent on local sea conditions. As sea levels continue to rise, the continuation of flood management practice in the form of artificial openings for ICOLLs will become challenging due to a decrease in hydraulic gradient between the ICOLL and the sea. Eventually, in order to be able to open Lake Ellesmere/Te Waihora to flow into the sea, the current predefined trigger value will have to increase in height relative to local sea level rise. In the short-term future, this will result in an increase in the risk of temporary inundation of adjacent land. In the long-term future, the increase of the ICOLL artificial opening trigger levels will result in permanent loss of adjacent land and the displacement of communities. A quantitative risk assessment was carried out to determine the effects of sea-level rise on Lake Ellesmere/Te Waihora’s artificial opening trigger levels in the short-term (10 to 30 years) and longer-term (50 to 100 years). This quantitative risk assessment was also able to determine the probable risk of permanent inundation of adjacent land. Geographic Information Systems were used to create contour maps showing the increase in Lake Ellesmere/Te Waihora’s current summer and winter artificial opening trigger levels in response to future sea-level rise. These maps are used to determine who will be affected by increasing amounts of sea level rise. Additionally, a qualitative risk assessment was undertaken to assess the level of preparedness of Lake Ellesmere/Te Waihora’s communities that have been identified to be at risk of inundation as a result of the anticipated increase in the lake’s water levels.Item Upscaling of point-scale groundwater recharge measurements using machine learning: A case study in New Zealand and Colombia(Lincoln University, 2019) Rios Rivera, Manuel AlejandroEstimating groundwater (GW) recharge rates is essential for water resources decision-making, in particular for dynamic regional-scale allocation. Typically, recharge has been estimated either based on models that require observed historic climatic and soil data for calibration or through measurements at a lysimeter monitoring site. Lysimeters are known as the most direct method of measuring drainage, yet utilization for decision making in regional water management is limited as merely point-scale measures of recharge are provided. In the past, machine learning techniques such as artificial neural networks (ANNs) have been found robust for modelling nonlinear hydrologic processes in relation to groundwater management. For this study, an ANN was selected in order to evaluate whether decision making in groundwater allocation can be improved by upscaling lysimeter-measured recharge. Model uncertainty for the ANN scheme was estimated employing a “Dropout” Monte Carlo (MC) technique. The ANN was trained and assessed in terms of its predictive performance to match lysimeter-measured recharge. The ANN was trained on daily time scale, employing recharge data recorded at three lysimeter stations in the Canterbury plains of New Zealand i.e. Dorie, Dunsandel and Methven sites. The best model in terms of accuracy and parsimony, provided R² values ranging from 0.65 up to 0.86 and a mean absolute error ranging from 0.41 to 0.99 when tested at the three lysimeter locations, with a model uncertainty of 6%. The model was implemented in a geographic information system (GIS) environment, in order to predict the spatial variability of land surface recharge, but also to calculate GW allocation for three of the groundwater allocation zones of the Canterbury Region (i.e. Rakaia-Selwyn, Ashburton and Chertsey). GW available for allocation was estimated to be approximately 650 * 106 m³ year⁻¹ or the Rakaia-Selwyn allocation zone; whereas allocation limits of 284.41 * 106 m³ year⁻¹ and 332.45 * 106 m³ year⁻¹ were estimated for Ashburton and Chertsey respectively. The suitability of applying an ANN to estimate LSR in a comparably data scarce region in Colombia was also tested. The results support how the inclusion of lysimeter data into the analysis, improves our confidence regarding the estimation of groundwater recharge. The methodology developed in this study couples a supervised machine learning technique i.e. ANNs with a visualisation tool in a GIS to predict land surface recharge employing rainfall, potential evapotranspiration and dominant soil texture data as inputs. The tool developed here can be utilised to provide support to water managers in order to identify sustainable dynamic regional groundwater allocation strategies.Item Investigation of nutrient management trade-offs using the Land Utilisation Capability Indicator (LUCI). A Canterbury, New Zealand, case study(Lincoln University, 2019) Gowera, Grace TariroAlthough agricultural productivity aims to meet global food demand, its expansion and intensification has led to an increase in nutrient load in waterways affecting water quality. This places farmers under pressure in controlling nutrient loss and conserving ecosystem services. The Land Utilisation Capability Indicator (LUCI) model can assist farmers in meeting freshwater policy requirements and identifying where changes on current land management can be done. LUCI is an ecosystem service modelling tool that illustrates the impacts of various ecosystem services. The model was applied in the Selwyn catchment to identify trade-offs between agricultural productivity and water quality. Trade-off results highlighted the possibility of improving water quality at the expense of agricultural productivity. However, to minimise loss of agricultural land or productivity, LUCI identified specific positions within the catchment which require nutrient mitigation. The study also modified the LUCI model. Without any alterations, LUCI uses soil type to determine nutrient loads in a catchment. Modifications done enabled land use to determine nutrient loads. The modifications included adding the Selwyn catchment farm data into the Land Cover Database (LCDB4), assigning export co-efficient (EC) values to different farm types in the study area. LUCI uses the export coefficient approach to calculate nutrient load of an area. Results from the modification process identified dairy farmers as major contributors of nutrient load.