use of baseflow indices to delineate baseflow dominated and … · 2016. 3. 8. · volume 57 2015...

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Volume 57 2015 CANADIAN BIOSYSTEMS ENGINEERING 1.1 Use of baseflow indices to delineate baseflow dominated and rapid response flow dominated watersheds Ramesh Rudra 1* , Imran Ahmed 1 , Alamgir A. Khan 1 , Kamal G. Singh 1 , Pradeep K Goel 2 , Mohammad Khayer 1 and Trevor Dickinson 1 1 School of Engineering, University of Guelph, Guelph ON N1G 2W1 Canada 2 Ontario Ministry of Environment and Climate Change, 125 Resources Road, Toronto ON M7A 1N3 Canada * Email: [email protected] http://dx.doi.org/10.7451/CBE.2015.57.1.1 Received: 2015 June 25, Accepted: 2015 July 23, Published: 2015 July 30. INTRODUCTION The separation of stream hydrographs into a baseflow component and a rapid response component has been of interest to researchers for decades. The water resource managers to address a variety of water quantity and quality issues, particularly as the relative magnitude of these components can vary quite widely from watershed to watershed. The traditional method to separate the baseflow is to analyze the discharge records (Arnold and Allen 1999, Arnold et al. 1995; Aksoy et al. 2009; Wang and Cai 2010). Determining the relative contributions of baseflow and surface runoff is often of prime importance for the selection of watershed management strategies and techniques associated with development projects; and the water quality variables needing most attention in a watershed are closely linked to the sources of flow e.g. suspended sediment and phosphorus being commonly linked to surface runoff. There is no direct way to continuously measure baseflow throughout a basin. Consequently, many approaches have been developed to estimate or separate baseflow from streamflow continuously in time (Rutledge 1998; Wittenberg 1999; Chapman 1999; Arnold and Allen 1999; Piggott et al. 2005; Eckhardt 2004). Regression models have the advantage of being easily implemented to estimate baseflow with reasonable accuracy (Ahiablame et al. 2013; Zhu and Day 2009). Several computer-based methods have been developed more recently for the separation of baseflow from stream hydrographs and associated baseflow indices. Baseflow index is defined as the ratio of long term mean baseflow to the total streamflow (Beck et al. 2013; Eckhardt 2008). These indices have been used alone, or in relation to selected watershed variables, for the estimation of the baseflow component of watershed yield in gauged and un-gauged watersheds (Beck et al. 2013; Lacey et.al. 1998; Mazvimavi et al. 2004; Neff et al. 2005; Eckhardt 2008). In a recent study, Zhang et al. (2013) applied two-parameter recursive digital filter method to determine baseflow index in Michigan (USA). Meshgi et al. (2014) using empirical equation to approximate baseflow time series using Genetic Programming (GP) and a groundwater numerical model for an urban watershed in

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Page 1: Use of baseflow indices to delineate baseflow dominated and … · 2016. 3. 8. · Volume 57 2015 CANADIAN BIOSYSTEMS ENGINEERING 1.1 Use of baseflow indices to delineate baseflow

Volume57 2015 CANADIANBIOSYSTEMSENGINEERING 1.1

Use of baseflow indices to delineate baseflow dominated and rapid response flow

dominated watersheds Ramesh Rudra1*, Imran Ahmed1, Alamgir A. Khan1, Kamal G. Singh1,

Pradeep K Goel2, Mohammad Khayer1 and Trevor Dickinson1

1School of Engineering, University of Guelph, Guelph ON N1G 2W1 Canada 2Ontario Ministry of Environment and Climate Change, 125 Resources Road, Toronto ON M7A 1N3 Canada *Email: [email protected] http://dx.doi.org/10.7451/CBE.2015.57.1.1

Received: 2015 June 25, Accepted: 2015 July 23, Published: 2015 July 30.

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INTRODUCTION The separation of stream hydrographs into a baseflow component and a rapid response component has been of interest to researchers for decades. The water resource managers to address a variety of water quantity and quality issues, particularly as the relative magnitude of these components can vary quite widely from watershed to watershed. The traditional method to separate the baseflow is to analyze the discharge records (Arnold and Allen 1999, Arnold et al. 1995; Aksoy et al. 2009; Wang and Cai 2010). Determining the relative contributions of baseflow and surface runoff is often of prime importance for the selection of watershed management strategies and techniques associated with development projects; and the water quality variables needing most attention in a watershed are closely linked to the sources of flow e.g. suspended sediment and phosphorus being commonly linked to surface runoff. There is no direct way to continuously measure baseflow throughout a basin. Consequently, many approaches have been developed to estimate or separate baseflow from streamflow continuously in time (Rutledge 1998; Wittenberg 1999; Chapman 1999; Arnold and Allen 1999; Piggott et al. 2005; Eckhardt 2004). Regression models have the advantage of being easily implemented to estimate baseflow with reasonable accuracy (Ahiablame et al. 2013; Zhu and Day 2009). Several computer-based methods have been developed more recently for the separation of baseflow from stream hydrographs and associated baseflow indices. Baseflow index is defined as the ratio of long term mean baseflow to the total streamflow (Beck et al. 2013; Eckhardt 2008). These indices have been used alone, or in relation to selected watershed variables, for the estimation of the baseflow component of watershed yield in gauged and un-gauged watersheds (Beck et al. 2013; Lacey et.al. 1998; Mazvimavi et al. 2004; Neff et al. 2005; Eckhardt 2008). In a recent study, Zhang et al. (2013) applied two-parameter recursive digital filter method to determine baseflow index in Michigan (USA). Meshgi et al. (2014) using empirical equation to approximate baseflow time series using Genetic Programming (GP) and a groundwater numerical model for an urban watershed in

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Singapore conducted a study. The results based on three parameters: minimum daily baseflow of the entire period, watershed area, and variation in groundwater table showed that this approach is better for baseflow estimation for an un-gauged watershed without stremflow discharge. Li et al. (2014) simulated two different filters and found that the Lyne and Hollick (LH) filter performs relatively better than the Boughton and Eckhardt filters, for a range of physical conditions at watershed scale. However, the various separation methods produce widely varying estimates of baseflow indices (Eckhardt 2008). Gan et al. (2015) used automated digital filter method of baseflow separation using historical daily streamflow data and fed by rainfall, snowmelt, and glacier melt, and reported that the baseflow index, with 65% variability, was expressively correlated with catchment climatic factors and aquifer properties. Factors that promote infiltration and recharge of subsurface storage will increase baseflow, while factors associated with higher evapotranspiration (ET) will reduce baseflow. Therefore, there is a need to explore the possible relationship of these baseflow indices with the physiographic and physical characteristics of watershed for the separation of stream hydrograph into a slow response component and a rapid response component. Therefore, the specific objectives of the study was i) to evaluate and compare the commonly used six baseflow separation methods for application in Southern Ontario conditions, and ii) to delineate baseflow dominated and rapid response flow dominated watersheds by relating baseflow indices with the physiographic and physical characteristics of a watershed.

MATERIALS AND METHODS The six commonly used methods; digital filtration technique (Nathan and McMohan 1990), PART (Rutledge 1998), United Kingdom Institute of Hydrology (UKIH) (Piggott et al. 2005), local minima, base sliding, and base fixed methods (Pettyjohn and Henning 1979) were selected, and are described here briefly. Digital filter method The recursive digital filter method is the most common and the simplest one to separate baseflow from the daily streamflow records (Nathan and McMahon 1990). This method is used for signal analysis and processing to separate high frequency (direct runoff) signal from low frequency (baseflow) signal. The following equation is used for digital filter method:

(1)

where, fk = the filtered quick response at the kth sampling

instant, yk = the original streamflow, α = the filter parameter (0.925), yk- fk = the filtered baseflow.

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PART method The PART computer program is a hydrograph-separation technique to estimate baseflow from the streamflow record. The PART program computes baseflow from the stream-flow hydrograph by first identifying days of negligible surface runoff and assigning baseflow equal to streamflow on those days; the program then interpolates between those days. PART locates periods of negligible surface runoff after a storm by identifying the days meeting a requirement of antecedent-recession length greater than “N” (time in days after which surface runoff ceases) and rate of recession less than 0.1 log cycle per day, and uses linear interpolation to connect across periods which do not meet those tests. UKIH method The United Kingdom Institute of Hydrology (UKIH) method is based on the identification and interpolation of turning points within an input time series of streamflow, and is used for daily average data. The turning points indicate the days and corresponding values of streamflow where the observed flow is assumed to be entirely baseflow. To calculate the turning points, the streamflow data are partitioned into a sequence of five-day segments and the minimum values of streamflow within each segment, an x and y pair where xi is the day on which the minimum value of flow of yi occurred, are selected and defined to candidate turning points. Each candidate turning point is then compared to the minima for the previous and subsequent segments. Turning points are examined using the condition 0.9yi ≤ min (yi-1, yi+1). The temporal variation of baseflow is estimated by piecewise linear interpolation bracketed by successive pairs of turning points. Local minima method Local minima method searches the hydrograph for the minimum streamflow during an interval 2N days. The width of the interval 2N used for hydrograph separation is the nearest odd integer (between 3 and 11) to twice the value of N. The value of N is the approximate duration of surface runoff from Linsley et al. (1982):

N = A!.! (2) where, N is the time after which surface runoff ceases, days; A is the watershed area, square miles. The local-minimum method checks each day to determine if it is the lowest discharge in one half the interval minus 1 day [0.5(2N-1) days] before and after the day being considered. If it is, then it is local minimum and is connected by straight lines to adjacent local minimums. Baseflow for days between local minimums is estimated by linear interpolation. Base sliding method Base sliding method also searches the hydrograph for the minimum streamflow during an interval 2N days. The width of the interval 2N used for hydrograph separation is the nearest odd integer (between 3 and 11 days) to twice the value of N. N is the approximate duration of surface runoff and is related to the watershed area by the equation

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N= (A)0.2 Linsley et al. (1982): N = A!.! (3) where, N is the time after which surface runoff ceases, days; and A is the watershed area, square miles. The base sliding version centers the interval 2N on the day of interest. Baseflow for that day is assigned the minimum streamflow within the interval; then the interval is moved forward 1 day, and the process is repeated. Base fixed method Base fixed method searches the hydrograph for the minimum streamflow during an interval of 2N days like local minima and base sliding methods. The width of the interval 2N used for hydrograph separation is the nearest odd integer (between 3 and 11) to twice the value of N. The value of N is the approximate duration of surface runoff from Linsley et al. (1982):

N= (A)0.2 (4) where, N is the time after which surface runoff ceases, in days; and A is the watershed area, in square miles. The base-fixed method assigns the lowest discharge to all days in the interval 2N, starting with the first day of streamflow record; then the analysis is moved forward 2N days, and the process is repeated. For this study, N equal to 5 days was used for all six methods.

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COLLECTION OF DATA Streamflow data Environment Canada’s HYDAT database website has about 1000 gauge stations in Ontario with historical streamflow data. From this historical data archives, 115 stations in Southern Ontario were selected on the basis of three criteria: 1) the flow regime should be identified as non-regulated; 2) there should be a minimum of ten years of continuous flow data; and 3) there should be very few missing data in the flow record. The locations of the 115 stations in Ontario, which met these criteria, are shown in Fig.1. The locations of the 115 stations in Ontario, which met these criteria, are shown in Fig.1. In historical time series of 115 gauging stations, so many stations had missing data for few days to few months and few years. Since baseflow separation model is only executable for continuous streamflow time series; therefore, to overcome this issue, any missing data were filled with the help of previous days, months, or years’ data as required. This approach also helped in relatively realistic separation of baseflow for the entire period with continuous dataset. Physiographic data The Ontario Ministry of Agriculture and Rural Affairs (OMAFRA) provided the digital format of physiographic

Fig.1. Map of Southern Ontario with station/watershed locations.

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data of Southern Ontario. The digital map was prepared using ARC GIS 9.2 software using the five major regions described in “The Physiography of Southern Ontario” by Chapman and Putman (1984). The selected 115 watersheds were clipped with this map to extract physiographic information relating to each watershed. Soil type and drainage class data Soils data in digital format were also provided by OMAFRA and Canadian Soil Information System (CANSIS 2005). The selected 115 watersheds were overlayed with this soil map to extract the soil group and drainage class information.

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Slope data The slope data was collected from CANSIS (2005). The slope classes are divided as: less than 4%, 4 - 9%, 10 - 15%, 16 - 30%, and more than 30%. To calculate the slope, a GIS boundary was used to clip the watersheds, then “area weighted average” was computed to get the slope class value for the watershed. The data are available for whole Ontario; however, the limitation of data was the slope classes were too crude. Land use data The land use data were collected from Canada Soil Information System (2005). The data were divided into

Fig. 2. Streamflow hydrograph and baseflow hydrograph by a) Digital filter method b) PART method c) Local minima method d) UKIH method , e) Base fixed method and f) Base sliding method for Nith River near Canning for water year 1979-80.

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Bedrock depth The only source of bedrock depth data available was from Atlas Canada. These data were able to provide an estimate of an average value of bedrock data for a watershed as no reliable source available for whole of Ontario. To calculate

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mixed Forest, shrub land, un-vegetated surface, marshland, grassland, fen, deciduous forest, coniferous forest, bog, agricultural crops, wetland, and water. The GIS boundary was used to clip the watersheds to reclassify as agriculture, forest, water, wetland, and others.

Fig. 3. Annual BFI frequency distribution of 115 watersheds in Southern Ontario for by a) Digital filter method b) PART method c) Local minima method d) UKIH method, e) Base fixed method and f) Base sliding method.

Table 1. Frequency Distribution Statistics for 115 Southern Ontario watersheds. Statistics Baseflow Separation Method Digital Filter PART Local Minima UKIH Base Sliding Base Fixed Mean 0.39 0.46 0.60 0.63 0.72 0.72 Median 0.38 0.47 0.62 0.66 0.75 0.75 Mode 0.26 0.53 0.71 0.71 0.78 0.82 Range 0.59 0.69 0.55 0.67 0.55 0.55 Min./Max. 0.13/0.72 0.12/0.81 0.31/0.86 0.28/0.95 0.40/0.95 0.39/0.95 Standard Deviation 0.14 0.18 0.14 0.16 0.13 0.13 Skewness 0.18 -0.03 -0.29 -0.28 -0.55 -0.55 % Above BFI ≥ 0.5 26.0 43.5 71.5 75.7 93.0 93.0

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the average bedrock depth for the watershed, first geo-referenced the digitized bedrock map to compute bedrock elevations for each watershed, and then surface elevations were computed using DEM (elevation data), provided by OMAFRA. Finally, bedrock elevation was subtracted from surface elevation to get “bedrock depth”.

RESULTS AND DISCUSSION Comparison of baseflow separation methods A computer program was developed to calculate baseflow indices (BFI) from six baseflow separation methods as per the equations provided earlier in one hundred and fifteen watersheds in Ontario conditions having more than 10 years of streamflow data. Each method produces different value of baseflow index. Analysis was carried out using the continuous flow data for each calendar year; however, values were also plotted for various seasons to show the seasonal variability in baseflow flow methods. A representative example of streamflow/baseflow hydrograph analysis is shown in Fig. 2. The digital filter and PART method generated the lowest volume of baseflow. While base sliding method and base fixed method produce highest volume of baseflow. Both UKIH and local minima methods produce moderate volume of baseflow in between lowest and highest BFIs. Overall, all six separation methods respond to long duration and high magnitude flashy peaks, and the lowest volume of baseflow is generated by digital filter method and the highest volume of baseflow by base sliding method. In the study, the long duration and high magnitude flashy peaks were the high flow values observed for longer period relative to normal baseflow values. These are typically observed during the winter and spring periods. This is due to snowmelt runoff and/or due to winter rainfall on frozen

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grounds. Under short duration and low magnitude flashy peaks, the digital filter baseflow does not change; PART method shows little increase in baseflow while all other methods show significantly high volume of baseflow. Baseflow hydrograph generated by digital filter method appears to be more realistic than any other methods, and its baseflow recession curve follow the exponential decay function associated with storage depletion. Analysis of frequencydistribution for annual baseflowindices(BFIs)The frequency distributions for each separation methods are presented in Fig. 3 with associated statistics summarized in Table 1. The frequency distributions reveal that the BFI values obtained from all six separation methods are highly dispersed, the range being essentially 0.60 and the standard deviation 0.15 for all methods. Such dispersion reflects the wide range of baseflow versus rapid runoff conditions likely occurring across the province, given the wide range of geologic, physiographic and hydrologic conditions. The central tendency of the frequency distributions is dramatically different from one baseflow separation method to another. The Digital Filter and PART methods yielded the smallest amounts of baseflow, with mean and median BFI values in the order of 0.40; the Base Sliding and Base Fixed methods yielded the highest amounts of baseflow, with a BFI central tendency value of 0.70; and the Local Minimum and UKIH methods yielded intermediate mean and median values of about 0.60. That is, individual baseflow estimates determined by the Local Minimum and UKIH methods were on average 50% greater than individual estimates determined by the Digital Filter and PART methods; and baseflow volumes estimated by the Base

Table 2. Correlation statistics of BFI for the application of six baseflow separation methods to stream flow data in Southern Ontario.

Digital Filter PART Local Minima UKIH Base Sliding Base Fixed

Digital Filter 301 26 23 19 18 17

1.002 0.90 0.89 0.73 0.65 0.65

303 29 28 26 25 25

PART 30 25 23 22 22 1.00 0.96 0.93 0.86 0.86 30 29 27 17 27

Local Minima 30 24 23 23 1.00 0.93 0.86 0.86 30 28 27 27

UKIH 30 28 28 1.00 0.98 0.98 30 29 29

Base Sliding 30 30 1.00 1.00 30 30

Base Fixed 30 1.00 30

1 Number of watersheds with the 30 highest BFI values common to both methods 2 Correlation coefficient for BFI values calculated by both methods for 115 watershed stream flow records selected in Southern Ontario 3 Number of watersheds with the 30 lowest BFI values common to both the methods

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Sliding and Base Fixed methods were on average 75% greater than baseflow volumes estimated by the Digital Filter and PART methods. Since the baseflow indices are arbitrary and true values are unknown, it is not possible to conclude which methods yield the most accurate estimates. However, it is important to acknowledge how different the baseflow estimates can be on the basis of separation method alone.

The skewness statistics for the BFI frequency distributions determined by the various baseflow separation methods are also quite different: from a somewhat positive value of 0.18 for the Digital Filter method to increasingly negative values for the other five methods, from – 0.03 for PART to – 0.55 for the Base Sliding and Base Fixed methods. Somewhat similar skewness values and distribution of watershed under different BFI categories as shown in Fig. 3 indicate similarities in some of these methods. For example, skewness values for both Base Fixed method and Base Sliding method is -0.55, and this is also reflected in Fig. 3 (e and f). Both these methods have predicted almost similar number of watershed in different BFI categories. Similar pattern is evident for PART and Local Minima methods. Further, these differences, together with those in central tendency, impact the percentage of the frequency

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distributions above a BFI value of 0.50, noted in Table 1. These percentages can be seen to vary dramatically, from 26% for the Digital Filter method to 93% for the Base Sliding and Base Fixed methods. These results reveal that the method yielding the smallest amounts of baseflow (i.e. Digital Filter) identifies about 75% of the study watersheds in southern Ontario to be rapid flow response dominated; while the methods yielding the largest amounts of baseflow (i.e. Base Sliding and Base Fixed) identify almost 95% of the watersheds to be baseflow dominated. Therefore, when separation methods yield substantially different individual estimates of baseflow, the overall perspectives of the relative contributions of baseflow and rapid flow response indicated by the BFI frequency distributions determined by the different methods can also be very different. Relative baseflow index (BFI) values The correlation coefficient between two sets of data is a good indicator of the similarity in the rank order of values in those data sets i.e., a high correlation coefficient is an indication that the rank orders are quite similar. The correlation coefficients presented in Table 2 for the BFI data sets determined using the six baseflow separation methods studied can be seen for the most part to be very high, suggesting that the rank order of watersheds as determined by the BFI values are quite similar for each method. Confirmation of this result is given by the number of watersheds with the highest and lowest thirty BFI values common to each pair of separation methods, also shown in Table 2. Twenty-five or more of the thirty lowest ranked watersheds were found to be common for all the separation techniques, and seventeen or more of the thirty highest ranked watersheds were found to be common.

These relative ranking results can be considered in relation to the frequency distributions presented in Fig. 3 to explore the likelihood of flows being dominated by baseflow or rapid flow response at least for the watersheds exhibiting the highest and lowest BFI values determined by the various methods. As noted above, all baseflow separation methods distinguish essentially the same watersheds to have the thirty lowest BFI values. For four of the methods, i.e., Digital Filter, PART, Local Minimum and UKIH, twenty-seven or more of the lowest ranked watersheds have BFI values < or = 0.50 (as revealed in Fig. 3). Eight of these watersheds were also determined to have the lowest BFI values of less than 0.50 by the Baseflow Sliding and Baseflow Fixed methods. Therefore, one can be reasonably confident that the watersheds commonly ranked by the various methods to have the thirty lowest BFI values are dominated by rapid flow response i.e., the baseflow is likely to be less than 50% of the stream flow. The watersheds discerned by the various baseflow separation methods to have the thirty highest BFI values are not quite as likely to be common. However, thirty or more of the watersheds studied were determined to have BFI values > or = 0.50 by all six separation methods. Therefore, although the watersheds distinguished

Table 3. Physiographic units dominant in watersheds with highest and lowest BFI values.

Physiographic Characteristics for Watersheds

With 30 Highest BFI Values With 30 Lowest BFI Values

Waterloo hills St. Clair clay plains Norfolk sand plain Haldimand clay plain Horseshoe moraines Huron slope Niagara escarpment Stratford till plain Dundalk till plain Horseshoe moraines South slope South slope Oak Ridges moraine Oak Ridges moraine Simcoe uplands Mount Elgin ridges Flamborough plain Ekfrid clay plain Algonquin highlands Peel plain Iroquois plain Stratford till plain Georgian Bay fringe Glengarry till plain Peterborough drumlin field Russell & Prescott sand plains Guelph drumlin field Ottawa Valley clay flats Ottawa Valley clay flats Iroquois plain Muskrat lake ridges Waterloo hills Dummer moraines Dundalk till plain Bruce Peninsula Oxford till plain Simcoe lowlands Carden plain Simcoe uplands

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by the various methods to have the highest BFI values were not totally common, one can be quite confident that they are all likely to be baseflow dominated streams. Possible relationships of BFI with physiographic characteristics and hydrologic soil groups To explore possible linkages between the relative BFI values and physiographic and soil characteristics, the dominant physiographic units and hydrologic soil groups

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were identified for each of the watersheds studied. The drainage classes were also pooled as poorly drained and well drained soils. The watersheds with the highest thirty BFI values ranged from: 0.51 to 0.72 for Digital Filter, 0.52 to 0.77 for PART, 0.66 to 0.86 for Local Minimum, 0.66 to 0.86 for UKIH, 0.73 to 0.89 for Base Sliding, and 0.73 to 0.89 for Base Fixed methods and the result (Table 3) reveals that the physiographic units found to be

Fig. 4. Location of 30 lowest BFI watershed determined by UKIH method in Southern Ontario.

Fig. 5. Location of 30 highest BFI watershed determined by UKIH method in Southern Ontario.

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dominant in the watersheds with the highest thirty BFI values (as determined by the Digital Filter Method) include primarily very well-drained features, e.g. sandy hills and plains, sandy moraines and drumlins. On the other hand, the watersheds with the lowest thirty BFI values ranged from: 0.13 to 0.28 for Digital Filter, 0.12 to 0.34 for PART, 0.31 to 0.51 for Local Minimum, 0.28 to 0.54 for UKIH, 0.40 to 0.73 for Base Sliding, and 0.39 to 0.72 for Base Fixed methods. The dominant in the watersheds with the thirty lowest BFI values include primarily poorly-drained features e.g. clay and till plains and moraines, and stratified clay and till. However, as some of the physiographic units include both well-drained and poorly-drained characteristics e.g. Horseshoe moraines, South slope, the Oak Ridges moraine, these units appear in watersheds with both high and low BFI values. Therefore, it becomes difficult to rely on physiographic units to distinguish watersheds dominated by either baseflow or rapid response flow.

The soils have been divided into four hydrologic soil groups (HSGs) based on soil infiltration capability by USDA Natural Resources Conservation Service (NRCS). The hydrologic soil groups (A,B,C, and D) were combined as A plus B as one group, and C plus D as the other group and the base maps used (Figures 4 through 6) were developed by distinguishing two categories of hydrologic soil groups (HSGs): a category of soils having moderate and high infiltration rates when thoroughly wetted were classified into hydrologic soil groups A and B; and a category of soils having low and very low infiltration rates when thoroughly wetted were classified

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into hydrologic soil groups C and D. Fig. 4 reveals the locations of the watersheds which were determined to have the thirty highest BFI values (as determined by the Digital Filter Method); Fig. 5, the locations of the watersheds determined to have the thirty lowest BFI values; and Fig.6, the locations of the watersheds with the fifty-five intermediate BFI values. It is clear from these figures that: (1) the watersheds with the highest BFI values are located in areas dominated by soils falling in the A and B hydrologic soil group categories; (2 the watersheds with the lowest BFI values are located in areas dominated by soils falling in the C and D categories; and (3) watersheds with intermediate BFI values are located primarily in areas with a mix of A, B, C and D soils. In other words, for the range of watershed flow characteristics present in Southern Ontario, and the ranges of BFI values associated with hydrographs emanating from these watersheds, a simple mapping of soils into those with relatively high infiltration rates (i.e. HSGs A and B) and those with relatively low infiltration rates (i.e. HSGs C and D) identifies very well watersheds with the highest and the lowest BFI values respectively. Since as noted above, the watersheds in southern Ontario with the thirty highest BFI values may be considered to be baseflow dominated, and those watersheds with the thirty lowest BFI values rapid flow response dominated, thus the mapping of HSGs for southern Ontario provides an excellent indication of locations where stream flow can be expected to be baseflow or rapid response flow dominated. This study is a step forward for better understanding the baseflow separation methods and its relationship with watershed characteristics.

Fig. 6. Location of 55 medium BFI watershed determined by UKIH method in Southern Ontario.

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CONCLUSIONS The baseflow index (BFI) calculated for a watershed is highly dependent on the method used for that calculation, various methods of calculating the BFI yielding very different values. Since the actual percentage of baseflow for a watershed is unknown, the method for calculating the BFI, which provides the most accurate estimate of BFI, is unknown, and it is unwise to rely on any single determination of BFI to obtain a reliable estimate of the percentage of baseflow for a watershed.

If several methods are used to calculate BFI values for a watershed, one can distinguish whether the watershed is baseflow or rapid response flow dominated by the definition of the base flow index (BFI). If all or most of the methods yield BFI values >0.5, one can be reasonably sure that baseflow contributes a majority of the flow for that watershed; and if all or most of the methods yield values <0.5, a majority of the flow is likely attributable to surface runoff or at least rapid response flow.

If one method is used to calculate BFI values for several watersheds in a region, one can expect to make reliable statements regarding the relative volume of baseflow yielded by the watersheds i.e., watersheds exhibiting the highest BFI values are likely to yield more baseflow than watersheds with the lowest BFI values.

In a region where various methods of determining BFI are found to yield a wide range of values, e.g. southern Ontario, groupings of watersheds exhibiting the highest and lowest BFI values may be used in concert with drainage classes such as Hydrologic Soil Groups to distinguish watersheds that are baseflow dominated from those yielding primarily rapid response flow.

ACKNOWLEDGEMENT The study was funded by Joint Nutrient Management Program from the Ontario Ministry of Environment and Climate Change (OMECC) and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). We would also like to thank Amanjot Singh, Water Quality Engineer, Credit Valley Conservation Authority, Mississauga, Ontario, for developing the computer program to analysis stream flow data.

REFERENCES Ahiablame, L.I., B.E. Chaubey, K. Cherkauer and V.

Merwade. 2013. Estimation of annual baseflow at ungauged sites in Indiana USA. Journal of Hydrology 476: 13–27.

http://dx.doi.org/10.1016/j.jhydrol.2012.10.002 Aksoy, H., I. Kurt and E. Eris. 2009. Filtered smoothed

minima baseflow separation method. Journal of Hydrology 372(1–4): 94–101.

http://dx.doi.org/10.1016/j.jhydrol.2009.03.037 Arnold, J.G., P.M. Allen, R. Muttiah and G. Bernhardt.

1995. Automated baseflow separation and recession analysis techniques. Ground Water 33(6): 1010–1018. http://dx.doi.org/10.1111/j.1745-6584.1995.tb00046.x

20

Arnold, J.G and P.M. Allen. 1999. Validation of automated methods for estimating baseflow and ground water recharge from streamflow records. Journal of the American Water Resources Association 35: 411–424.

http://dx.doi.org/10.1111/j.1752-1688.1999.tb03599.x Arnold, J.G. and P.M. Allen. 1999. Automated Methods

For Estimating Baseflow And Ground Water Recharge From Streamflow Records. Journal of the American Water Resources Association 35: 2. http://dx.doi.org/10.1111/j.1752-1688.1999.tb03599.x

Beck, H.E., A.I.J.M.V. Dijk, D.G. Miralles, R.A.M.de Jeu, L.A. Bruijnzeel, T.R. McVicar and J. Schellekens. 2013. Global patterns in base flow index and recession based on streamflow observations from 3394 catchments. Water Resources Research 49: 1–21. http://dx.doi.org/10.1002/2013WR013918

Chapman, L.J. and D.F. Putnam. 1984. Physiography of Southern Ontario. Ontario geological survey, Special Volume 2.

Chapman, T. 1999. A comparison of algorithms for stream flow recession and baseflow separation. Hydrological Processes 13(5): 701–714.

http://dx.doi.org/10.1002/(SICI)1099-1085(19990415)13:5<701::AID-HYP774>3.0.CO;2-2

Eckhardt, K. 2004. How to construct recursive digital filters for baseflow separation. Hydrological Processes 19(2): 507–515.

http://dx.doi.org/10.1002/hyp.5675 Eckhardt, K. 2008. A comparison of baseflow indices,

which were calculated with seven different baseflow separation methods. Journal of Hydrology 352: 168-173. http://dx.doi.org/10.1016/j.jhydrol.2008.01.005

Environment Canada. HYDAT. 2005. http://www.wsc.ec.gc.ca/products/main_ e.cfm?cname = products e.cfm.

Canadian Soil Information System. 2005. Soil Landscape of Canada Version 3.1. Canadian Soil Information System, Agricultural and Agri-Food Canada.

Gan, R., L. Sun and Y. Luo. 2015. Baseflow characteristics in alpine rivers — a multi-catchment analysis in Northwest China. Journal of Mountain Science 12(3): 614-625.

http://dx.doi.org/10.1007/s11629-013-2959-z Lacey, G.C. and R.B. Grayson. 1998. Relating baseflow to

catchment properties in south-eastern Australia. Journal of Hydrology 204:231-250.

http://dx.doi.org/10.1016/S0022-1694(97)00124-8 Li, L. H.R., Maier D. Partington, M.F. Lambert, and C.T.

Simmons. 2014. Performance assessment and improvement of recursive digital baseflow filters for catchments with different physical characteristics and hydrological inputs. Environmental Modelling & Software 54: 39–52.

http://dx.doi.org/10.1016/j.envsoft.2013.12.011

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Volume57 2015 CANADIANBIOSYSTEMSENGINEERING 1.11

21

Linsley, R. K., M. Kohler, A and J.L.H. Paulus. 1982. Hydrology for Engineers. McGraw-Hill New York, USA

Mazvimavi, D., A.M.J. Meijerink and A. Stein. 2004. Prediction of baseflows from basin characteristics: a case study from Zimbabwe. Hydrological Sciences 49(4): 703-715.

http://dx.doi.org/10.1623/hysj.49.4.703.54428 Meshgi, A., P. Schmitter, V. Babovic and T.F.M. Chui.

2014. An empirical method for approximating stream baseflow time series using groundwater table fluctuations. Journal of Hydrology 519: 1031-1041. http://dx.doi.org/10.1016/j.jhydrol.2014.08.033

Nathan, R.J. and T.A. McMahon. 1990. Identification of homogeneous regions for baseflow and recession analyses. Journal of Hydrology 121: 217-238. http://dx.doi.org/10.1016/0022-1694(90)90233-N

Neff, B.P., S.M. Day, A.R. Piggott and L.M. Fuller. 2005. Report 2005-5217. Baseflow in the Great Lakes Basin. U.S. Geological Survey Scientific Investigations.

Pettyjohn, W. A., and R. Henning. 1979. Preliminary estimate of ground-water recharge rates, related streamflow and water quality in Ohio. Report No 552, 323pp. Ohio State University Water Resources Centre.

22

Piggott, A.R., S. Moin and C. Southam. 2005. A revised approach to the UKIH method for the calculation of baseflow. Hydrological Sciences Journal 50(5): 911 -920. http://dx.doi.org/10.1623/hysj.2005.50.5.911

Rutledge, A.T. 1998. Computer programs for describing the recession of ground-water discharge and for estimating mean ground-water recharge and discharge from streamflow data-update. Report 98-4148. U.S. Geological Survey Water Resources Investigations.

Wang, D. and X. Cai. 2010. Recession slope curve analysis under human interferences. Advances in Water Resources 33(9): 1053–1061.

http://dx.doi.org/10.1016/j.advwatres.2010.06.010 Wittenberg, H. 1999 Baseflow recession and recharge as

nonlinear storage processes. Hydrological Processes 13: 715-726. http://dx.doi.org/10.1002/(SICI)1099-1085(19990415)13:5<715::AID-HYP775>3.0.CO;2-N

Zhang, Y., L. Ahiablame, B. Engel and J. Liu. 2013. Regression modeling of baseflow and baseflow index for Michigan USA. Water (5): 1797-1815. http://dx.doi.org/10.3390/w5041797

Zhu, Y.H and R.L. Day. 2009. Regression modeling of streamflow, baseflow, and runoff using geographic information systems. Journal of Environmental Management 90: 946–953.

http://dx.doi.org/10.1016/j.jenvman.2008.02.011