iM o u n t H e l e n C a m p u sS c h o o l o f S c i e n c e , E n g i n e e r i n g a n dI n f o r m a t i o n T e c h n o l o g yBachelor of Engineering – Civil(Honours)Research Project Thesis2019Rainfall Trends in the Victorian CentralHighlandsS u b m i t t e d b y : A n d r e w R o b bS t u d e n t I D : 3 0 3 2 0 0 0 1S t r e a m : C i v i l E n g i n e e r i n gS u p e r v i s o r : A n d r e w B a r t o nD a t e : 3 1 / 1 0 / 2 0 1 9iiAbstractThe study of rainfall is important as it can show the changes in characteristics andany trends that may be present. Rainfall is subject to many different factors thataffect the amount that will fall within an area, these factors include large scale factorssuch as El Nino and La Nina and more local effects such as the climate of an area.With factors like these that are subject to change there can be a high amount ofvariation within rainfall data when looking a long period. This variation in rainfalls cancause issues if a change is prolonged for example the millennium drought which wasan extended period of below average rainfalls causing droughts. Understanding theeffects of changing rainfall characteristics may allow for a better understanding howthese change in rainfall characteristics effect an area.This research uses rainfall from four separate locations within the centralhighlands spanning 88 years to study any variations during this period. This data isused within selected statistical tests to try and observe any variations amongstdifferent rainfall characteristics, to visualize the results of these test Microsoft Excelis used to create graphs and tables showing the results for all tests. These resultshave been used to identify any changes or trends that may have occurredthroughout the study period.iiiAcknowledgementsI would like to acknowledge and thank my Supervisor Andrew Barton who hasprovided me with guidance and assistance throughout each stage of writing mythesis.Declaration of OriginalityI certify that except where due acknowledgement has been made, the work is thatof the author alone; the work has not been submitted previously, in whole or in part,to qualify for any other academic award; the content of the thesis is the result of workwhich has been carried out since the official commencement date of the approvedresearch program,; and, any editorial work, paid or unpaid, carried out by a thirdparty is acknowledged.Andrew Robb31/10/2019ivContents1 Introduction……………………………………………………………………………………………. 1Overview …………………………………………………………………………………………. 1Current assumptions …………………………………………………………………………. 3Literature review……………………………………………………………………………….. 41.3.1 Introduction………………………………………………………………………………… 41.3.2 Area………………………………………………………………………………………….. 51.3.3 Hydrology ………………………………………………………………………………….. 61.3.4 Climate and climate change …………………………………………………………. 71.3.5 Statistics and data ………………………………………………………………………. 81.3.6 Impacts……………………………………………………………………………………… 9Problem Statement …………………………………………………………………………. 102 Methodology ………………………………………………………………………………………… 13Selecting stations……………………………………………………………………………. 142.1.1 Selecting method………………………………………………………………………. 142.1.2 Chosen locations ………………………………………………………………………. 15Data ……………………………………………………………………………………………… 152.2.1 Data collection ………………………………………………………………………….. 152.2.2 Data Organisation……………………………………………………………………… 16Statistical tests ……………………………………………………………………………….. 172.3.1 Annual Exceedance Probability …………………………………………………… 172.3.2 Probability Distribution Function/ Normal Distribution……………………… 172.3.3 Mass curve ………………………………………………………………………………. 182.3.4 Weather Anomaly graph…………………………………………………………….. 192.3.5 Mann-Kendall/ Sens slope………………………………………………………….. 193 Results………………………………………………………………………………………………… 23vBeales Reservoir…………………………………………………………………………….. 233.1.1 Average Recurrence Interval ………………………………………………………. 233.1.2 Normal Distribution ……………………………………………………………………. 243.1.3 Mass Curve ……………………………………………………………………………… 253.1.4 Anomaly…………………………………………………………………………………… 263.1.5 Mann-Kendall/ Sens Slope …………………………………………………………. 26Kirks Reservoir……………………………………………………………………………….. 283.2.1 Average Recurrence Interval ………………………………………………………. 283.2.2 Normal Distribution ……………………………………………………………………. 293.2.3 Mass Curve ……………………………………………………………………………… 303.2.4 Anomaly…………………………………………………………………………………… 313.2.5 Mann-Kendall/ Sens Slope …………………………………………………………. 31Lake Bolac …………………………………………………………………………………….. 333.3.1 Average Recurrence Interval ………………………………………………………. 333.3.2 Normal Distribution ……………………………………………………………………. 343.3.3 Mass Curve ……………………………………………………………………………… 353.3.4 Anomaly…………………………………………………………………………………… 363.3.5 Mann-Kendall/ Sens Slope …………………………………………………………. 36Moonambool ………………………………………………………………………………….. 383.4.1 Average Recurrence Interval ………………………………………………………. 383.4.2 Normal Distribution ……………………………………………………………………. 393.4.3 Mass Curve ……………………………………………………………………………… 403.4.4 Anomaly…………………………………………………………………………………… 413.4.5 Mann-Kendall/ Sens Slope …………………………………………………………. 414 Discussion …………………………………………………………………………………………… 425 Conclusion…………………………………………………………………………………………… 466 References ………………………………………………………………………………………….. 48viList of FiguresFigure 1, Climate Map of Australia (Bureau of Meteorology, 2001)………………………. 1Figure 2,location of data recording stations (Jones, Wang, & Fawcett, 2009)………… 5Figure 3,Temperature Anomaly Graph (Bureau of Meteorology, 2019) ………………… 8Figure 4, Timeline of Ballarat water storage (Barton. A, 2016)…………………………… 12Figure 5, Method flow Diagram …………………………………………………………………….. 14Figure 6, Station Location Map …………………………………………………………………….. 15Figure 7, Average Recurrence Interval Beales Reservoir …………………………………. 23Figure 8, Normal Distribution Beales Reservoir ………………………………………………. 24Figure 9, Mass Curve Beales Reservoir…………………………………………………………. 25Figure 10, Anomalies Beales Reservoir …………………………………………………………. 26Figure 11, Average Recurrence Interval Kirks Reservoir ………………………………….. 28Figure 12, Normal Distribution Kirks Reservoir ……………………………………………….. 29Figure 13, Mass Curve Kirks Reservoir………………………………………………………….. 30Figure 14, Anomalies Kirks Reservoir ……………………………………………………………. 31Figure 15, Average Recurrence Interval Lake Bolac………………………………………… 33Figure 16, Normal Distribution Lake Bolac……………………………………………………… 34Figure 17, Mass Curve Lake Bolac ……………………………………………………………….. 35Figure 18, Anomalies Lake Bolac………………………………………………………………….. 36Figure 19, Average Recurrence Interval Moonambool……………………………………… 38Figure 20, Normal Distribution Moonambool …………………………………………………… 39Figure 21, Mass Curve Moonambool …………………………………………………………….. 40Figure 22, Anomalies Moonambool……………………………………………………………….. 41List of TablesTable 1, Mann-Kendall and Sen’s Slope Beales Reservoir ……………………………….. 27Table 2, Mann-Kendall and Sen’s Slope Kirks Reservoir ………………………………….. 32Table 3, Mann-Kendall and Sen’s Slope Lake Bolac………………………………………… 37Table 4, Mann-Kendall and Sen’s Slope Moonambool……………………………………… 4211 IntroductionOverviewThe Victorian central highlands is an area west of Melbourne consisting of sixseparate local councils, shires and rural cities these are Ballarat city council,Pyrenees shire, Ararat Rural city, Hepburn shire, Moorabool shire and the GoldenPlains (Regional Development Victoria, 2019). All of these combined take up a totalarea of 14,687 km2 making it the second smallest region within Victoria, with thelarger of the regions consisting of areas as large as 41,546 km2 (RegionalDevelopment, 2019). While this is a relatively small area when compared to otherVictorian regions the placement of stations within this area can still have varyingresults due to Victoria’s high climate variability (State of Victoria, 2016).Figure 1, Climate Map of Australia (Bureau of Meteorology, 2001)2Australia has a large variety of climates that varies even in small areas, this canbe seen in figure 1 which shows the variation of the climates across Australia andthe variations within these climates. Victoria is no different consisting of grass landsand varying temperate climates, resulting in varying rainfall characteristics across thestate. The climate within the central highlands consists of varying temperate climatesand a small portion of grass land towards the northern side. Temperate arecharacterized as climates without extremes of temperature or precipitation, thechanges between summer and winter do not sway between extremes. The amountof sway between the two can be related to the proximity to the ocean as the moreinland temperate climates will have more variation where a close proximity will havemore consistent characteristics (Audubon, 2019). However, the area is stillsusceptible to extreme events such as drought and flooding with the most recentexample of this being the Millennium Drought which lasted from 1996 to 2010 andhas been described as the worst drought on record (Climate Council of Australia,2015), the opposite of this, flooding is not often as wide spread but still has adramatic effects, a recent example of flooding happened in the years following theMillennium Drought in 2010 and 2011 where Victoria suffered from its worst floodson record (Australian Broadcasting Corporation, 2014). Climate change has had andcontinues to have an impact on climate within Victoria and Australia, these changes,both Victorian and globally, have manifested to date as a mix of gradual and stepchanges (Yilmaz & Perera, 2015).Previous study into rainfall trends within Victoria have been conducted by Yilmazand Perera (2015), In this study Victorian extreme rainfall trends were investigatedusing 23 stations from across the state for 8 different storm durations. The resultsfrom this study shows how even though stations are within the same area the resultsbetween the station can vary and for the same storm duration there are stations thathave positive and negative trends within the studied area. The durations that werestudied also affect the amount of stations showing positive or negative trends, withthe amount of stations that show a positive trend decreasing and the number ofdecreasing trends increasing with longer durations.3Current assumptionsWith climate change being such a big discussion point in terms of its impacts, it isimportant to understand Victorian climate and how it is changing. As already stated,Victoria has a high climate variability and has experienced numerous floods andprolonged droughts, with greenhouse gas effects and other changes to the globalclimate system, changes to Victorian climate influences have occurred. It has alsobeen found in the latest climate research from the Victorian climate initiative thatthere has been a clear reduction in cool season rainfall over recent decades (Stateof Victoria, 2016). It may be assumed that the data from all the chosen stations willfollow this trend or a similar trend, however as can be seen in previous studies suchas Hajani and Rahman (2018) that trends from all stations within an area will notshow the same results that agree with what is expected there can be a high amountof variation in terms of the calculated trends. It is even possible that no or aninsignificant trend is found for the stations.Currently the planning of water resources, agriculture, irrigation and associatedinfrastructure is based off being able to characterize variations of two key variables:stream flow and precipitation (Sun, Roderick, & Farquhar, 2018). This is where theassumption of stationary climate becomes relevant as the traditional approach tocharacterizing future events is to assume that the future will resemble the past (Lins& Cohn, 2019), or in other words the natural systems fluctuate within an unchangingenvelope of variability. However the idea of stationary climate is now beingchallenged due to substantial human driven climate change affecting averages andextremes of precipitation, evapotranspiration and rates of discharge in rivers (Milly etal., 2008). As this study deals with precipitation data the stationarity of the resultscan be checked to see if they agree or disagree with the stationary climateassumption.4Literature review1.3.1 IntroductionStudies are conducted regularly to gain a greater understanding of the chosentopic, with future studies expanding on current knowledge, for example the study ofrain fall trends within selected areas. Rainfall trends are used to show, based on asection of data consisting of date and recorded rainfall, if an area is receiving greateror lesser amounts of water through precipitation. This is based on if a trend ispositive, negative or insignificant this can be expanded further through statisticalanalysis of the data used.This kind of information is not consistent across the world and varies greatlybased on the time and location that is being studied, with the same state showingdifferent results depending on where and what time period is being studied. Previousstudies that have been conducted show such information, such as studies conductedfor the NSW area by Hajani, Rahman, and Ishak (2017) and Hajani and Rahman(2018). It is important to look at where the studies have been conducted as theremay be gaps in areas that could be filled in with further research.As rainfall is a major factor in the study of hydrology affecting multiple aspectssuch as surface water, floods, catchments and the hydrological cycle it is importantto have an understanding of the topic. This does not mean of studying all aspectsjust the topics affected by rainfall. This may not all be directly relevant to rainfalltrends although it can help give a better understanding of how rainfall trends couldcan have impacts on catchments and other areas.Climate is a major factor that affects the amount of rain an area will receivethroughout the year. It is expected that an area of tropical climate will receive ahigher recorded rainfall for a year when compared to a desert climate, however withthe effects of climate change elements such as average temperatures and rainfallshave been affected. An example of this is the southeast of Victoria where there hasbeen drought in recent years, as there has been a decline in rainfall and a higherdaily maximum temperature (Murphy & Timbal, 2008).5The methods of analyzing rainfall trends have been developed for many years toprovide an array of different methods that can be used to identify trends and to showwhat kind of trend it is. For instance, there is the Mann-Kendall test which is a verycommon trend test used regularly across many studies, this test also has variationsallowing it to calculate different factors of a trend. To accomplish this time series datais required, which in this case will be represented in the form of rainfall data, theresults of these calculations can show current and past rainfall trends allowingspeculations of the impacts that they have had and are currently having.1.3.2 AreaStudies for rainfall trends have been conducted across the world that shows whatthe rainfall trends currently are and have been in the past. To be able to study anareas rainfall trends the appropriate data must be accumulated, in Australia thiscollection is conducted by organizations such as the Bureau of Meteorology throughrecording stations. These recording stations cover all of Australia with varyingconcentrations as can be seen in figure 2, this figure shows the location of theFigure 2,location of data recording stations (Jones, Wang, & Fawcett, 2009).6recording stations across Australia. These stations record data that allows studies ofthe weather to be conducted including rainfall trend analysis. With the assistance ofsuch data, studies have been conducted in locations all over Australia such asstudies completed within NSW (Hajani & Rahman, 2018; Hajani et al., 2017) usingmultiple rain stations as data points. There has also been studied carried out acrossVictoria (Yilmaz & Perera, 2015) which used selected stations across the state,breaking it down into regions and selecting some stations from each region to get awide area of coverage. With this in mind there is room to conduct studies that arerelated to a smaller specific area to give a more in depth look of a localized area,such as a study of the area of the Victorian central highlands region to expand on theknowledge of Victorian rainfall trends.1.3.3 HydrologyRain fall is recognized as a very important part of the hydrological cycle and afactor of climate change (Worden, Noone, & Bowman, 2007). Changes to theamount of rain fall will influence many aspects of hydrology, as rain fall is used inareas such as surface water hydrology, flood hydrology, catchments and thehydrological cycle.There have been previous studies on such topics for example the studyconducted by Ishak, Rahman, Westra, Sharma, and Kuczera (2013) where annualflood maximums were studied through analysis of rainfall data. Areas of hydrologythat rely on knowing rainfall within a desired area, consist of but are not limited to thedesign of catchment and stormwater systems, with both being affected by theamount of rain received and the runoff of an area. With the further development ofland into impervious surfaces resulting in increasing runoff old stormwater systemspreviously implemented struggle to manage the increased flows (Burns, Fletcher,Walsh, Ladson, & Hatt, 2012). If old storm water systems are not capable of handlingincreased runoff due to impervious surfaces knowing what the rainfall was when itwas designed and what they currently are can be used to find a more suitablemethod of handling stormwater rather than just adding the new onto the old.71.3.4 Climate and climate changeRainfall is an important part of an areas climate with hotter dryer climates likedeserts receiving an average of less than 250 mm of rain per year (Petersen, 2019),and wetter climates such as temperate receive an average yearly rainfall of 800 mmof rain (Meteoblue, 2018). These amounts will not be exactly precise for each yearas they just give an idea of the rainfall of the climates. Australia is a great example ofa country with varying climates with figure 2 showing the variation of the climatesacross the country.The Australian hydro-climatic time series is known to have one of the greatestvariabilities when compared to other continents (McMahon, Finlayson, Haines, &Srikanthan, 1992). This natural variability happens over a number of different timescales from annual through to multi-decadal.Three well know climatic modes know for this are the Southern annular mode, ElNino Oscillation and Interdecadal Pacific Oscillation (Hendon, Thompson, &Wheeler, 2007), all three of these modes affect the climate of an area and in turnaffect the rainfall. another climatic factor that affects rainfall is climate change due toelements like a higher concentration of greenhouse gases within the atmosphere,company’s Such as the Commonwealth Scientific and Industrial ResearchOrganization (CSIRO) have done research into such areas. With an uncertainty as tothe ability to restrict future greenhouse gas emissions scientists have run differentclimate models containing varying amount of greenhouse gasses to see possibleoutcomes, these outcomes show that with a high concentration of CO2 there will behigher temperatures and lower amount of rainfall with high chances of extreme dailyrainfalls (CSIRO, 2017). With the chance of rainfalls varying in future it would bebeneficial to see current and past performances of rain through studies such asrainfall trend analysis.Trends can be identified in other aspect of an area’s climate such as thetemperature, a method of doing this is to create a temperature anomaly graph andlook at the changes that are occurring. Information such as this can be found on theBureau of Meteorology website as shown in figure 3, this figure shows the anomalygraph for Australia beginning form 1910 until current date. Figure 3 shows a steadyincrease in the average temperature with the anomaly’s following this increasing8trend with the higher and lower anomaly’s increasing in value across the time series(Bureau of Meteorology, 2019).Figure 3,Temperature Anomaly Graph (Bureau of Meteorology, 2019)1.3.5 Statistics and dataWith Australia suffering from drought and serious climatic extremes in recentyears the need for high-quality climate information has arisen to assist in placingthese events in proper historical perspective and to provide a context forunderstanding the associated impacts on humans and the environment (Jones et al.,2009). In figure 2 is the location of recording stations that provide information byrecording environmental data such as rainfall, temperature, humidity and vaporpressure. Records such as these have been taken in locations for many years forinstance the data collected at Beales reservoir which has a data record starting from1889 (“SILO | LongPaddock | Queensland Government,” 2018). Some recordlengths are not as long as not all stations were in place as early as the previousexample as it is a long-standing station in the area, other stations in a similar areamay not have data records that go as far back such as White swan reservoir that hasa data record length going back until 1953 (Australian Bureau of Meteorology, 2018).It is very important that all data being used for calculations are of a high quality asto get accurate and reliable results. That is why it is important to use a trusted source9of environmental data such as the Australian Bureau of Meteorology that qualitytests their data for errors that may have occurred during the recording of data. Theseerrors could be a result of equipment being damaged, a station being upgraded/downgraded or even observer absence, the recognition of data on days such asthese is important to ensure that the data is accurate and not a false representationof the events.1.3.6 ImpactsChanges in rainfall amount can have impacts on many different areas such aswater management, climate, surface water and agriculture. With these impactsvarying depending on the location and how much rainfall the area would normallyreceive, it is important to have an understanding of this information to asses thatactual impact an area may be experiencing. Knowing the changes in precipitation ofan area is considered to be one of the most critical factors in determining the impactsof climate change and variability on the environment (Khan, 2015). The hydrologicalcycle is one of the most notable areas to be impacted by climate variability andclimate change, if there is a change in the climate behavior it can result in changes inthe magnitude and frequency of hydrological events (Xu, Gong, Jiang, Chen, &Singh, 2006). With changes such as these old storm water and similar systems maynot be able to handle the increase of inflows due to increased rain fall magnitude andan increase of impervious surfaces due to further development (Burns et al., 2012),resulting in systems being overtaxed and not working as they were designed. As theclimate is constantly changing causing varying impacts on natural and humansystems, with this variation over time and region it is important to have regularexamination and research (Hajani & Rahman, 2018), with proper monitoring theimpacts of climate change may be managed more efficiently rather than dealing withthe repercussions.Other impacts that are felt regularly in Australia are droughts which have variedlength due to temperature and rainfalls and floods which can have varying affectsthat range from large floods that causes damage to infrastructure and costs millionseach year to small floods that are an inconvenience (Khan, 2015). The presence of aperiod of drought puts a strain on the water supply of an area causing the potential tofail to supply (Sankarasubramanian, Lall, Souza Filho, & Sharma, 2009), an example10of this is already happening in Cape town where the water supply is running out andapproaching day zero (Wright, 2018). Day zero is the day that taps will be turned offand residents of the town will be required to go to 1 of 200 water collection points(Winter, 2018). This is an extreme case of drought however this is always apossibility due to increasing temperatures and elongated periods of low rain. Theopposite of this being floods which also has a major effect on communities with thecost of damages caused by rainfalls annually can be as high as $150 million (Hajaniet al., 2017). Flood are also a common natural disaster that could happen any timethere is a significant rainfall within a short period of time (Hajani et al., 2017) theoccurrence of floods is also affected by the ground conditions such as the existingmoisture content of the soils.Problem StatementA rainfall trend analysis is the study of the rainfall within an area using datacollected over as many years as is available, this data is analyzed mathematicallythrough a variety of methods to indicate changes in rainfall trends for the selectedstudy area. “Trend analysis has been used to understand the effects of climatechange and variability in the past on extreme rainfall events”(Yilmaz & Perera, 2015).Having this understanding of past changes in rainfall event characteristics is criticalto provide reliable prediction of future change (Min, Zhang, Zwiers, & Hegerl, 2011).Rainfall trends can have a significant effect on water infrastructure and floodprotection structures due to varying intensity and frequency, trends can also be anindicator of non-stationary climate (Yilmaz & Perera, 2015).The data used to identify trends is currently collected by organizations such as theAustralian bureau of meteorology, local water management authorities andQueensland government managed, Scientific Information for land owners (SILO) adata base of climate records. These data records are taken by recording stations atvarious locations such as white swan reservoir, quality of data collected at thestations is very important factor when selecting which stations will be used. Stationsshould be considered for its location, length of records and quality of data, forexample amount of data gaps, these gaps can be filled in through various methodssuch as regression analysis(Hajani & Rahman, 2018). However, if data gaps are toofrequent the station would be excluded from the study.11Rainfall trend analysis indicates trends within rainfall data, these trends can showan increase or decrease within chosen areas. This could be seen in the form of astep down in average rainfall at a certain point in time. These results vary greatly dueto factors such as uncontrollable environmental events, location of study, seasonand climate change.One of the most critical factors in determining the impacts of climate change of anarea is the change in precipitation (Khan, 2015). Climate change is currently a majorconcern of the recent years knowing what effects it has had and is having on rainfallcould be a useful tool in determining how bad the current effects are, futuremonitoring of rainfall trends could be an indicator of how implemented strategies arecounter acting climate change and how effective they are.Rainfall can have many impacts including natural disasters such as floods thatcan cause significant economic damage as well as being a danger to human life(Hajani et al., 2017). With there being a possible increase in rainfall intensities as aresult of climate change there will a corresponding increase in flood risk. Theseextreme rainfall event can also be an indicator of non-stationary climate; currentdesign rainfall intensities are used in the design of water infrastructure and floodprotection projects. These intensities are derived from the stationary climateassumption (Yilmaz & Perera, 2015), that the probability of occurrence of an extremerainfall event is not dependent on time (Bonaccorso, Cancelliere, & Rossi, 2005).This however may not be true if a trend is observed in a rainfall series (Khaliq,Ouarda, Ondo, Gachon, & Bobée, 2006). Another major impact of a change inrainfall is a drought, which is usually found to be a combination of high temperaturesand low rainfall (Ishak et al., 2013) which can extend for years causing more serverdroughts. These effects have recently been felt in Australia with the 2000’s droughtthat affected most of the country, and example of these effects can be seen in figure4 which show Ballarat water storage capacity and how it was affected during thedrought and following years.12This graph shows the affect the drought had on the water storages of Ballarat,along with the following wet period and then to varying amounts of rain withuncertainty on if it will continue to be dry, wet or if it will hold constant. This can haveimpacts on many parts of everyday life as well as agriculture, with theimplementation of water saving strategies such as water restrictions and a lack ofwater to maintain healthy crops. There has been previous modelling conducted thatshows that the effects of drought will only increase due to lower rainfall and moresevere temperatures (Kothavala, 1999). Australia is a great example of these twoimpacts as it has a high climate variability that can consist of sustained droughtsfollowed by periods of high rainfall resulting in flooding.Figure 4, Timeline of Ballarat water storage (Barton. A, 2016)13The specific area that I will be researching will consist of the Central Highlandsarea within Victoria, the method that will be used to look at trends and changes incharacteristics will be mathematical using computer programs to analyze largeamount of rainfall data from stations that I will select. These rainfall stations will berequired to have a record period that will show a reasonable history of rainfall andnot just a short glimpse, they will also have to have a mostly complete data set thathas very few gaps that will need to be filled or may have already been filled. For themethod of analysis there may be more than one program used to analyze the data,this will depend on how much detail they can provide and my proficiency with them,currently two programs that are being considered are SPSS and Excel, these are notthe final choice of program they are just initial ideas. At the completion of the trendanalysis I will be able to present a full-time line of rainfall data from a starting datethat is determined. It is through this that the relative information of positive andnegative trends will be identified, and all questions can be answered. It will also fill inan area that has not previously been studied that could be added to a larger scalemap consisting of other studies conducted across Australia.2 MethodologyMy first step of researching the trends and changes in rainfall characteristics wasto collect rainfall data from around the central highlands area, this data had to meetcertain criteria for selection these criteria range from location to length of records.Once the data had been collected and organized the data was then used instatistical tests that show the changes of different rainfall characteristic and toidentify any trends present. This process consists of the selecting of the recordingstations, Data and statistical tests and results, with further discussion on conclusionspresented later.To Identify any changes in rainfall characteristics or trends and understand them atimeline of data that spans as long of a time series as possible is needed. Having atime period that spans a longer period allows the changes to be show over multiplesmaller timelines, this will also allow increasing and decreasing changes to be seen.These changes will be identified in the results and discussion sections as a result ofthe tests outlined within Statistical tests, to do this a variety of tests have been used14to try and identify different changes. Some of the tests that have been used alsooverlap with the information that they provide, this can provide some reassurancethat the tests have been done correctly and that the results are reliable.A crucial part in ensuring that the results are of these tests are reliable is theaccuracy of the data that is used for the test, if this data is inaccurate this will have adetrimental effect on the results rendering any finding useless.Method Flow Diagram:Selecting stations2.1.1 Selecting methodTo select the stations that were used for this study, criteria were set to ensure thatthe data and the produced results are reliable.The Initial criterion for selecting stations was that data needed to be taken from areliable resource, the location of stations relative to each other, the data had to havea length of at least 88 years and have a data set that is only missing a maximum of15% of its record. To meet the first criteria of using reliable data the SILO data basewas used, the data from this data base is provided by the Australian Bureau ofMeteorology and includes labels to show how the data was obtained i.e. actualrecording, deaccumulated from nearby stations and interpolated (“SILO |LongPaddock | Queensland Government,” 2018). To find stations that were insuitable locations the station location map of figure two was used with the stationscutdown to Victorian stations with at least 88 years of data and plotted onto googlemymaps, this allowed the location and data length to be easily visualized so that theappropriate stations can be chosen. As to give reliable results for stations thestations also needed to have a mostly complete data series, this was easilyaccounted for as the data that was put into mymaps included the percentage of datafor each station, making it a quick check to see if the chosen stations had adequatedata.Selecting Stations Data Statistical Tests ResultsFigure 5, Method flow Diagram152.1.2 Chosen locationsThe final stations that have been used for the purpose of this study are BealesReservoir, Kirks Reservoir, Lake Bolac and Moonambool, these stations met thecriteria that had been set therefore the data from these stations is what has beenused to complete the statistical tests.Figure 6, Station Location MapData2.2.1 Data collectionThe rainfall data that was used for the purpose of the study was taken from theQueensland government managed SILO database, this data base containsinformation gathered form recording stations all across Australia. This informationincludes rainfall amounts, max and min temperature, evaporation and the date ofrecording provided by the Bureau of Meteorology (BOM). The BOM also providesrainfall and other environmental data and makes it available to the public so thiscould also be used. The only advantage of using one website over the other is thatthe SILO data base labels the rainfall data based on how it was gathered forexample whether it was the recorded rainfall, interpolated or based on nearbystations. Therefore, the SILO data base has been chosen to be used as the mainsource of data based on the fact that how the data was obtained is included. OnceMoonamboolLake BolacKirks Reservoir Beales Reservoir16the data for all stations has been obtained it can then be rearranged to only showrelevant information and be broken into the chosen time periods.2.2.2 Data OrganisationThe time periods that will be used for the purpose of this study have beendetermined using the information provided in Guidelines for Assessing the Impact ofClimate Change on Water Supplies in Victoria report. This document has beenproduced by the Victorian state government department of Environment, land, waterand planning, the document refers to a study into the climate change within Victoriabased on climate change models. These models were based on greenhouse gasemission scenarios provided by the IPCC fifth assessment report which has beenadopted in line with recent historical trajectory of greenhouse gas concentrations(State of Victoria, 2016). Taking this into mind a recommendation is made for asuitable time period that can be used in studies that takes into account appropriatelength as to capture enough natural climate variability and avoid effects of trendsover the baseline period. Other desired characteristics for the time period are listedas including a wide range of natural climate variability, the greenhouse gas inducedclimate change is reasonability stationary and is comparable across supply systemsand water corporations. The time period that is recommended to be used for acurrent climate base line is from July 1975 to date, the reason for this time period isthat it includes a wide range of natural climate variability including the millenniumdrought, 1982/83 drought and multiple wet years, it is also representative of currentlevel of greenhouse gases climate behavior and it differentiates between the levelsof global warming the has been seen in the past, currently and in the future (State ofVictoria, 2016).Therefore, for the purpose of this study the period of 1975-2018 will be used toshow current characteristics and 1931-1974 will be used to show pastcharacteristics. These periods will be further broken up into smaller time periods toshow a closer look of the past and present characteristics when run through thestatistical analysis. As these time periods are 44 years long. They will be broken intotwo 11-year periods this can then be used to see if there are any changes within thefour 11-year periods.17Statistical testsThe test that have been chosen for the purpose of this study have been used asthey are already established statistical test that have been used in previous studies,each of the test have been studied and refined leaving no extra work to manipulatethe methods to allow them to be used for this study. Not all of the tests arespecifically designed for the study of rainfall such as the mass curve however thetest can still be used without variation as it still shows the desired results.2.3.1 Annual Exceedance ProbabilityThe annual exceedance probability is the probability that a rainfall event willhappen in any year, this probability could be represented as a percentage or a one inx amount of years.The process of completing this test is relatively simple with the only input requiredbeing time series data, in this case daily rainfall, consisting of a recorded value andthe date of recording, that date of recording is only for the information purpose and isnot used in the calculations. The annual probability of exceedance is completed asfollows (Barton, 2014).
This data is then organised from largest to smallest and labelled as n1, n2,n3, … n∞.The final value in the series is also used as m for the calculations as this isthe total amount of data points within the series.
With the data organised the formula
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