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    The effects of hydrological and nutrient disturbance on stream invertebrate communities using a trait-based approach : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Aquatic Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2018) Dinh, Yen Thi Hai
    Anthropogenic altered flow regimes and nutrient enrichment can cause significant impacts on stream biota and may lead to species loss if characteristics of the local fauna are not compatible with the new environmental conditions. I used fourth corner models, Bayesian ordination, and regression analysis to assess those potential effects on trait and species composition of invertebrate communities in UK, New Zealand (NZ) and Vietnamese streams. NZ temperate mountain streams with greater substrate disturbance increased the abundance of plastron- respirers, but not those having two aquatic life stages or who were filter feeders. UK temperate rivers with predictable multiple high flows per year supported individuals having highly synchronized life history strategy; rivers with one prolonged rising climb and strong groundwater influence were better for those having a high reproduction strategy, and rivers with a steep peak flow supported both strategies. Nutrients affect functional feeding and life history traits via promoting algal overgrowth in NZ streams. Both periphyton biomass and nutrients increased the abundance of algae piercers, collectors and those having two aquatic life stages, being long-lived and having hermaphroditic ability; but decreased the abundance of shredders, scrapers, and those having univoltine life cycles. The post-flood recovery of invertebrate communities depended on the recovery of the food base of the food web that was, in turn, determined by the presence of a forest canopy cover and nutrient levels in a stream. Within the forest canopy stream, communities in the low nutrient site recovered by week 9 after a 1-in-50-year flood in Wellington, NZ. Without the forest canopy, the recovery of communities in nutrient impacted streams (by 25 weeks) was probably associated with a quicker regrowth of periphyton while communities in the low nutrient site had not recovered even after 40 weeks. Hydrological disturbances, nutrients, and their combination had strong effects on invertebrate communities in temperate streams. Taxa that survive in a site have trait characteristics that are highly compatible with both the hydrological and nutrient conditions at a site. In contrast to temperate invertebrate communities, Vietnamese tropical highland community structure was influenced more by elevation than disturbance. Further studies are required to clarify how flow disturbance may effect invertebrate communities in tropical streams.
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    Assessing water availability in the Oroua River Catchment : a thesis presented in partial fulfillment of the requirements for a Master Degree in Applied Science (Agricultural Engineering), Massey University
    (Massey University, 2002) Reyes, Mona Liza Fortunado de los
    The study estimated the 1993-1998 natural flows as well as their corresponding reliabilities along Kiwitea Stream and Oroua River upstream of the old Kawa Wool station. These estimates could present a baseline condition for assessing the hydrologic capability of the catchment for the existing rights and the amount of streamflow still available for additional rights. The study demonstrated that water availability modeling could be a useful tool in water resource management and planning for the Oroua catchment. The "usual" or high river flow allocation management for the Oroua River wherein a right may abstract water up to its permitted rates could be modeled in WRAP. The results of the simulation based on full abstraction of permitted rates suggested that on a monthly basis, there was enough flow physically available to meet all consented abstraction rights including the minimum flow requirement at Almadale and Spur Road stations throughout the 1993- 1998 simulation period. The study had identified an apparent shortcoming of the WRAP model in simulating the MWRC's water allocation schemes at times of low river flow wherein water rights are either restricted or curtailed whenever the flow reached the set monthly flow threshold and the minimum flow level. The WRAP program was lacking of a mechanism or algorithm that will allow a water diversion target to vary depending on a gauged flow at other locations. The study demonstrated that the criteria stipulated in the Oroua Catchment Water Allocation Regional Plan for rostering abstraction at times of low river flow could be accounted in WRAP water availability modeling using a weighted ranked priority scheme. The results of simulation apportioning the combined maximum abstraction rates for irrigation purposes, based on prior use and natural upstream-to-downstream location among irrigation rights, indicated a minimal increase in the utilization of available water of the Oroua River. Thus, with increased water use as a management objective, such options would not be an attractive alternative. To facilitate relevant hydrologic and institutional water availability and reliability assessment of the Oroua River, it is recommended that a modification be made in the WRAP program to include mechanism or algorithms that will allow automatic change of diversion target as a function of gauged flow. Also, a shorter computational interval, such as weekly or daily, would yield more relevant results for real-time water management for the Oroua River. For future simulation or modeling studies for the Oroua River, there is a need to have an actual streamflow measurement or gauging station downstream of the river for validation purposes. There is also a need to have data on actual abstractions and discharges to the Oroua River and its tributaries.
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    Application of Markov chain model in streamflow forecasting : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Geography at Massey University
    (Massey University, 1996) Mpelasoka, Freddie Simon
    This thesis presents an approach to streamflow forecasting based on a Markov chain model to estimate conditioned probabilities that a one time-step ahead streamflow forecast will be within a certain streamflow range. In this application a set of "states of flow" defined over streamflow ranges (intervals) forms a finite state space of a Markov chain. Flood forecasting is made by focusing on a preselected state of flow as a flood state. A multi-objective (two criteria) function for the quantification of the model performance is introduced. Specifically designed for a flood forecasting and warning system the two criteria are the probability of issuing a false alarm and the probability of failing to forecast a flood event. The goal is to minimize both criteria simultaneously together with a preference of accepting more false alarms than misses. The model has two options of making a forecast: (1) a Threshold Forecast (ThF) approach in which a forecast is based on the probability of making a one-step transition from any state into the flood state; (2) the Most Probable Event (MPE) forecast approach selects the state of flow where the next streamflow is most likely to occur. Forecasts being probabilistic, there are several options for deciding on when it is appropriate to issue a flood warning in the probabilistic framework. A search for the appropriate probability p0 is made on interval [0,1] through evaluation of the objective function at each p0, using data sets from three North Island catchments ( Akitio River, Makakahi River and Kiwitea Stream). The model applying the option of threshold forecasts performed generally well depending on the relative costs assigned to false alarms and misses. The model performed better on the Akitio River which has strongly fluctuating streamflows than on the Makakahi River and Kiwitea Stream which have relatively modest variations in flows. When the Model applied the option of the most probable event forecasts did not perform well as the probabilities of false alarms were found to be too high for the model to be accepted. The outcome of this study suggests a simple short-term flood forecasting procedure especially for rivers with strongly fluctuating flows.
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    Application of environmental weighting system for quantification of minimum flow in Whanganui River : a thesis submitted in partial fulfilment of the requirements for a degree in Master of Philosophy in Resource and Environmental Planning, Planning Department, Massey University
    (Massey University, 1994) Guinto, Rufino C
    Environmental weighting system is a technique for measuring the environmental sensitivity of reduced river flows. A points system with seven environmental categories was used to arrive at scores indicative of a location's sensitivity and commensurate with the maximum permissible volume of abstraction. The same score is used to estimate the environmentally prescribed flow or minimum flow. This study deals with the applicability of an environmental weighting system to the quantification of a prescribed minimum flow using the Whanganui River as a case study. The minimum flows in Whanganui River have been subject to considerable debate since the construction of a series of intakes on several headwater streams in the early seventies for the purpose of increasing water volumes for the ECNZ power generation at Tokaanu and nine hydroelectric power plant stations on the Waikato River. In 1977, the NZ Canoeing Association requested that a minimum flow be fixed which in 1983, culminated in a recommendation of 22 m-3 s-1 minimum flow at Te Maire in December and January. A review of these flows was carried out in 1987 and the minimum flow was increased to 29 m-3 -1 from December to May following a Planning Tribunal Hearing in 1989-90. The results showed that one of the flow allocation methods was very restrictive to ECNZ operations while strongly favouring the requirements of fisheries and other instream uses. Two other options were examined under the demand conditions in the Whanganui River. They provided for an environmentally prescribed flow which was similar to that proposed by the Planning Tribunal Determination (1990), but each had slightly different abstraction proposals to meet suggested flows. Under New Zealand conditions the technique was found to be useful in identifying the environmental constraints of competing demands for river water. However, in an already regulated flow regime the outcomes were hypothetical but still meaningful.
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    The use of radon and complementary hydrochemistry tracers for the identification of groundwater - surface water interaction in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at the Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Martindale, Heather
    Understanding how surface waters and groundwaters interact is an integral component of managing the influence of nutrient inputs to water quality. Knowledge of the potential nutrient loads from discharging groundwater is essential for meeting the bottom line nutrient concentrations in surface waters. Radon-222 is an emerging tracer for measuring groundwater-surface water interaction which has been underexploited in New Zealand. The aim of this research was to establish the potential of using radon for measuring groundwater and river water interaction in the New Zealand environment. Low and high resolution radon surveys were carried out in two gravel-bed rivers, the Hutt and Mangatainoka Rivers, in lower North Island of New Zealand. To provide accurate measurements of radon concentrations in surface waters containing very little radon, the development of a cost and time effective, simple and reproducible high sensitivity radon measurement method was investigated. Furthermore, the study aimed to assess the potential of using radon measurements in combination with concurrent stream flow gauging and other hydrochemistry data for providing more detailed information on groundwater and river water interaction processes. Radon measurements were found very helpful to identify groundwater discharge and recharge locations in both the Hutt and Mangatainoka Rivers. Furthermore, a high sensitivity radon analysis method was developed with a lower limit of detection of 0.006 BqL-1, a vast improvement on the direct count method, and offering practical advancements over previously published methods. This high sensitivity method was used to establish radon concentration thresholds to identify locations of groundwater discharge, potential groundwater recharge and hyporheic exchange in NZ gravel-bed rivers. In both studied rivers the groundwater discharge and potential recharge patterns identified by radon were not always matched by the concurrent flow gauging surveys, highlighting the ambiguity surrounding the use of concurrent flow gauging in gravel-bed rivers for mapping river gains and losses. In some sections of the studied rivers the concurrent flow gauging data indicated areas of groundwater recharge or discharge where the radon data showed the opposite process to be occurring. This has led to the conclusion that underflow beneath the gravels and other parafluvial exchange processes can cause the interpretation of concurrent flow gauging results to be misleading. Flow gauging combined with radon sampling gives a more conclusive picture of the groundwater and river water interaction processes in the gravel-bed rivers.
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    The impacts of reduced flow on instream habitat condition and macroinvertebrate behaviour : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2008) James, Alexander Bryan Wilfried
    The allocation of water and setting of minimum flows is a contentious issue. Despite this, there is little research into the impacts of reduced stream flows on instream habitat and biota. Previous studies tend to concentrate on fish or macroinvertebrate community structure with few studies investigating the behavioural responses of macroinvertebrates to flow reduction. Therefore the aim of my thesis was to assess the impact of severe flow reduction on habitat condition and macroinvertebrate behaviour (drift and refugia use) using before-after, control-impact (BACI) experimental manipulations in natural (Wairarapa, New Zealand) and artificial stream channels (Canterbury, New Zealand). Instream channels were also used to assess the impact of flow reduction duration and magnitude on macroinvertebrate community structure and vertical distribution in the substrate. Reduced flow tended to decrease depth, velocity, and wetted width and increase fine sediment deposition. However, the common assertion that it would lead to increased temperatures and lowered dissolved oxygen levels was not supported by my results, although this may occur in some streams. I found that severely reduced flow in small streams had minimal effect on water temperature, although it can depress nighttime dissolved oxygen minima. Flow reduction markedly increased the drift propensity of some taxa immediately following flow reduction, before it fell back to near background levels for the rest of the reduced flow period. This increased drift occurred as animals redistributed themselves to more suitable microhabitats within the stream. Additionally, flow reduction reduced the drift distance of animals making it unlikely that drifting would be a viable way of escaping low flow conditions. Flow reduction had no impact on the densities or vertical distribution of animals within the substrate, however, most species were present at all depths sampled in the hyporheic zone, providing a source of colonists should some event (flood or drying) denude the benthos of animals. An instream channel experiment showed that apart from changes to the relative abundances of a few common taxa, flow reduction magnitude (up to 98% reduction) had little impact on the macroinvertebrates of a lowland river. Overall, my results suggested that severe flow reduction stresses a number of taxa, causing them to drift as they redistribute themselves within the stream. I found no evidence that animals actively seek refuge in the hyporheic zone, and in a lowland river, the magnitude and duration of flow reduction had minimal effect on the macroinvertebrate community.