Patterns in River Flow Data

Patterns in River Flow DataIntroductionThe hydrologic response of a landmark is ground on interactions between landscape characteristics and climatic characteristics input as the disgrace property descriptors, geomorphologic descriptors, geologic descriptors and land use varies among protestent watersheds, the watersheds could oppose in truth differently to fall (Mohamoud, 2004). The main aim of this coursework is to assess the invasion of youthful modality variety show on river devolve to uncover its logical implication in affecting river move by analysing and comparing river guide records from depicted object River Flow Archive, and to lastlight and assess the discrepancys in the hydrologic response to mode convert of the lead chosen rivers with tell apart characteristics, located in the UK.The tercesome rivers chosen to be analysed includes the eastward Avon, the River dove and the River Greta, both with natural catchments (natural to at bottom 10% at Q95), with no known major artificial transfers to the catchment that would influence the watercourse of the rivers, in order to attempt to focus solely on the essence of clime change (CEH, n.d.). The catchments examined all comparable in size 83000m2 for River dove at Izaak Walton, located in central England 86100m2 for Greta at Rutherford Bridge, located in north- east England 85800m2 for tocopherol Avon at Upavon, located in south- west England (CEH, n.d.). formula 1 demonst put the locations of the trio gauging station on triad break apart maps of the UK (CEH, n.d.)Apart from the differences in location (figure 1.), there be too contrasting catchment characteristics. East Avon at Upavon predominantly consists of 64.5% of upper greensand and lower drinking glass of 27% the remaining 8.5% consists of middle chalk, upper chalk, clay, as wholesome as gault, positivistic river gravel and alluvium at the bottom of the valley (CEH, n.d.). In comparison, the Greta at Ruth erford Bridge catchment is known to be steep, and it in the main consists of millst mavenness grit (CEH, n.d.). Finally, in contrast, plunk at Izzak Walton is known to be long and narrow (CEH, n.d.). It mainly consists of mudstone, millstone grit and sandstone, with underlie carboniferous limestone forming the left hand watershed (CEH, n.d.). When looking at the catchment statistics in relation to the geology, East Avons catchment consists of 40.3% of towering permeability bedrock, with 59.7% moderate permeability bedrock (CEH, n.d.). In contrast, Greta and falls catchment consists of 100% of moderate permeability bedrock (CEH, n.d.). Besides the obvious difference in geology, the sites also vary differently in terms of their climatic characteristics, as shown in mesa 1.1, 1.2 1.3, and finally, land cover also varies among the triplet river catchments, as shown in table 2 (Met Office, n.d. CEH, n.d.). plug-in 1.1 averages table showing climate info for the England SE pri mal S District, which covers period 1981-2010 (Met Office, n.d.) turn off 1.2 averages table showing climate info for the Midlands District, which covers period 1981-2010(Met Office, n.d.) remit 1.3 averages table showing climate data for the England E NE District, which covers period 1981-2010(Met Office, n.d.)Table 2- Catchment statistics of Land Cover for distri besidesively of the three catchments (CEH, n.d.).MethodologyThe river melt data obtained from these three gauging stations, between the division of 1973 and 2013 were used for analysis. In order to come upon and identify lessen var. for each of the chosen sites, as well as to identify any change in the hydrological regime of the three rivers collectible to recent climate change at the sites, the three sets of river flow data from National River Flow Archive (NRFA) was first imported on to a spread sheet, where the flow measurement/ reading of each river were sorted in to order, according to the hydrological date of the measured flow. The data was then plan as followsDischarge vs. timeMonthly flow vs. timeA flow duration incline for flow frequency analysis remember send packing vs. Hydrological year Julian dateNext, visual inspection of the interprets was carried out, and the graphs produced for each river were directly compared to assess how seasonal and time series patterns of flow differ across the three sites, and to determine whether all three sites showed the same pattern of flow through time.Results and DiscussionIn order illustrate the seasonal river flow pattern in the three catchments figure 2 shows hydrographs for the three rivers. The location of these catchments is shown in figure 1, and characteristics are presented in the introduction. Upon inspecting the hydrographs, the following observations were do (points of reference are labelled as A on the hydrographs)East Avons loaded discharge rashs at 1.17 m3s-1, on solar daylight one hundred thirtyGretas squiffy disc harge peaks at 6.81 m3s-1, on day 69 falls blotto discharge peaks at 3.35 m3s-1, on day 82Figure 2-Hydrographs for three rivers, showing the mean discharge vs Hydrological year Julian date, plus a graph for comparison between the rivers mean discharge over daysAccording to a study on UK river flow regimes, Hannaford et al. (2012) had suggested that UK river flow regimes give the bounce be considered temperate precipitation/evapotranspiration dominated, preferably than snowmelt dominated. This means that the seasonal cycle will be mainly control by evapotranspiration, leading to high flows in wintertime and lower flows in summer, with the spring and autumn as transition seasons (Hannaford et al., 2012). When referring back to the peak discharge observations in a higher place, all three rivers conformed to the same general pattern, as day 82, 69 130- the days where the mean discharge has reached the peak for the three river all lies within the winter period, indicating that t he flow will be high during winter days. Further more(prenominal), the hydrographs also shows that, for all three rivers, the mean discharge appeared to be relatively low, and dupe all remained low between day 280 -320 for all three rivers (section B on the hydrographs), during the summer period.Figure 3- Monthly Discharge vs. Hydrological Year epoch graph for all three rivers, with a secondary axis correspond to the mean monthly discharge curveIn terms of the concord of the flow, figure 3 shows East Avons maximum minimum curve, and its mean curve look very correspondent- the curves are almost overlapping one an different which shows a low fluctuation in flow. This suggests that the flow of the river is very consistent. In contrast, the other twain rivers have less consistency. This sewer be observed when comparing the max, min and mean curve in Doves graph- the general shape of the curves are very similar to one another, yet there are a few points in the graph where there a re some very noticeable differences, where the mean curve tend to have a dandyer fluctuation and peaks at higher discharge points compared to the other devil curves, thus showing that it is generally consistent, but the consistency is lower compared to East Avon. Finally, Gretas corresponding graph displays great fluctuation although both max and mean curves are both similar and conforms to a similar pattern, it is clear that the min curve looks a mountain flatter, with a pattern that is not very similar to the other two curves within the graph. This indicates that Gretas consistency between years is relatively poor.Although all three river exhibit similar seasonal flow patterns, there are still notable difference in their response time. The natural event of discard time and the difference between the response times of the three sites commode be explained by the difference in the catchments physical characteristics and its underlying geology. When referring back to the peak di scharge data, East Avon displays a lagged response, peaking at day 130, as opposed to peaking at days closer to 82 and 69 (days of which Dove and Greta reached its peak). This substantial variation can caused by East Avons catchment geology, as it consists of 40.3% of high permeability bedrock, with 27% of chalk in the catchment, as opposed to 0% of high permeability bedrock in the other two catchments the high permeability bedrock and the highly permeable chalk means that groundwater storage plays a meaningful role in effecting the overflow regime of the East Avon catchment, which lead to East Avons discharge peaking at around February, towards the end of the winter period, as opposed to peaking towards the start of the winter period, like the other two rivers have.Next, in order to illustrate the cogitate behind Gretas earlier peak, in comparison to Doves later peak at day 82 (figure 2), the physical have got of both catchments must be examined in detail. Both catchments have an very(a) percentage of moderate permeability bed rock, and both are similar due to the fact that the catchments both consist of Millstone Grit. However, the topography are significant different between the two catchments. Since Gretas catchment is significantly steeper when compared to the Doves catchment, as illustrated in figure 6 and table 3, Greta will have a more responsive regime compared to Dove due to a quick run- off rate of precipitation. This could also provide an definition to why the mean discharge curve in the Greta hydrograph is subjected to a great level of daily variation in comparison to the other two sites and their respective hydrographs.Figure 4- Flow duration curves for all three sites, with an spare graph (bottom graph) combing the Q* data (Discharge Ratio where Q*= Q/Q50) of three sites for comparison- note that surpass of Q* is in Logarithmic Scale (Base10)Figure 5- Flow duration curves for all three sites, with an additional graph (bottom graph) comb ing the Q* data (Discharge Ratio where Q*= Q/Q50) of three sites for comparison- the scale of Q* has been adjusted to go from 0-6 for comparisonAdditionally, figure 4 shows that Gretas curve has the steepest incline, followed by Dove, and then by East Avon with the flattest slope. The observations mirrored those findings above precisely Gretas steepest slope indicates a highly variable river, and the flow mainly consists of direct runoff (Searcy, 1959). In contrast, curves with a flatter slope (e.g. East Avon with the flattest curve) which means they have a more constant flow, and can signify the existence of surface and/or groundwater storage in East Avons case, highly permeable chalk acts as storage for water, which equalized the flow of the river (Searcy, 1959). Furthermore, in figure 5, the graph also provides information on the three rivers frequencies of very high flows and very low flows. When employing the parameters of Q*=5 for high flow, and Q*=0.2 for low, the curves s hows that Greta exhibits a significantly lower affinity of time flow lower than the Q* of 5, whereas the curves for Dove and East Avon are very similar, with a much higher proportion of time flow less than Q* of 5, meaning that high flows occurs a roofy less frequently in Dove Avon in comparison to Greta. In terms of low flow, three rivers are all dissimilar in their frequency of low flow. Gretas proportion of flow less than 0.5 is 0.02, whilst Doves proportion is 0.16, with East Avons proportion is 0.34. East Avons higher proportion of time flow less than 0.5 means that the occurrence of low flow is more frequent in East Avon, and in comparison, Dove has got a relatively lower frequency of low flow, and Greta with the low frequency of low flow over the years within the standard period.Table 3- Elevation data for Greta and Doves catchment (CEH, 2014)Figure 6-Elevation social function of England. This map shows the significant difference in elevation between the brotherhood of England and the South of England. (Windpower Program, n.d)As seen in figure 7, the flows of all three rivers do seem to conform to a similar pattern over time, with no significant changes in the temporal pattern and frequencies of pig out/ droughts. However, upon further inspection, the graph shows that the magnitude of the floods for all three rivers had increased over time the high flow peaks have seemed to be higher in more recent years. This phenomenon can possibly be explained by global climate change as global temperature increase, this leads to an increase in water vaporing the atmosphere. As suggested by Milly et al. (2002 cited Das et al, 2013), Kunkel et al. (2013 cited Das et al., 2013) and Trenberth (1999 cited Das et al, 2013), storms are likely to come back more extreme peak precipitation rates, which can lead to more sharp floods around the globe (Groisman et al., 2005 cited Das et al, 2013). However, although the trend identified above is consistent with climate change, it is also consistent with variability driven jointure Atlantic Oscillation (Hannaford, 2013). With the significant knowledge gap in the accord of long term multi-decadal variability in flow driven by NAO, along with the lack of long term flow data easy for this report, it will be premature to attribute specific steam flow trends to anthropogenic climate change (Hannaford, 2013).Figure 7- Hydrograph showing change in river discharge between 1973- 2012Summary ConclusionIn conclusion, river flow regimes of the three assessed rivers are heavily dependent on catchment geological characteristics and climate. Climate plays a major role in effecting the flow, as the relatively temperate climate in England meant that the dominant factor in effecting flow regimes are precipitation/ evapotranspiration, which leads to the occurrence in flow variation between seasons as rate of evapotranspiration varies. In relation to climate, among the three rivers, there were observed changes in peak flow and flood magnitude over time, which global climate change might be responsible for, as it can lead to precipitation extremes, which in turns lead to more run-off and higher river flow. Besides that, variation in geology also contributes to the difference in hydrology of each river, as groundwater storage can affect the rate of run- off, which in turns affects the flow and the response of the three rivers. Finally, anthropogenic influences can affect flow regime of rivers (Schneider et al, 2013). However, there is no significant evidence to show how these had modified the flow of the rivers.ReferenceCentre for ecology Hydrology (n.d) 43014- East Avon at Upavon. National River Flow Archive. Map , Catchment comment Flow Record Retrieved from http//www.ceh.ac.uk/data/nrfa/data/peakflow.html?43014 (Last accessed on 07/11/2014)Centre for Ecology Hydrology (n.d) 28046 Dove at Izaak Walton.. 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