ABSTRACT Title of Thesis: A COMPARATIVE HYDROLOGIC ANALYSIS OF SURFACE MINED AND FORESTED WATERSHEDS IN WESTERN MARYLAND. Degree candidate: Timothy Lee Negley Degree and year: Master of Science, 2002 Thesis directed by: Dr. Keith N. Eshleman University of Maryland Center for Environmental Science This thesis presents the results of a hydrologic analysis conducted as part of a larger, multi-faceted, collaborative effort to study ecosystem function of a watershed subjected to surface mining and reclamation in the Appalachian Region of the United States. The primary goal of this study was to determine whether a small watershed subjected to surface mine reclamation practices (MAT 1) displayed a stormflow response to rain events that was different from those displayed by a young second-growth forested watershed (NEFl). A secondary goal was to investigate whether intensive surface mining in the Georges Creek basin has altered stormflow response at a larger river basin scale when compared to a similar, but predominantly forested basin (Savage River). At the small watersheds, MATl produced greater a) runoff coefficients (2.5x); b) total runoff (3x); and c) peak runoff rates (2x) compared to NEFl. Total rainfall explained 63% of the variation in total runoff at MAT I compared to only 21 % of the variation in total runoff at NEF I. Regardless of a recent 13% increase in surface mine reclamation in the Georges Creek basin, little difference in stormflow response was observed for 15 storms analyzed across the two larger basins. Georges Creek on average responded 3 hr more quickly than Savage River, However the hydrological response characteristics of the two basins were similar. In addition, hydrological response characteristics for Georges Creek and Savage River remained relatively stable over time. Further research is needed to address inabilities to scale responses observed at the small watersheds. , A COMPARATIVE HYDROLOGIC ANALYSIS OF SURFACE MINED AND FORESTED WATERSHEDS IN WESTERN MARYLAND. by Timothy Lee Negley Thesis submitted to the Faculty of the Graduate School of the University of Maryland at College Park in partial fulfillment of the requirements for the degree of Master of Science 2002 Advisory Committee: Dr. Keith N. Eshleman, Chair Dr. William S. Currie Dr. Philip Townsend ACKNOWLEDGEMENTS I would like to acknowledge first of all my committee members Drs. Keith Eshleman, William Currie, and Phil Townsend for their guidance, direction, and insightful comments on this thesis. Field and lab supprnt for this project was provided by: Jim Kahl (Maryland Department of Environment) and Roger Thomas (Natural Resource Conservation Service) who assisted in site se lection; Keith Eshleman, Mark Castro, Matt Kline, Jamie Welch, and Derek Wiley w10 assisted in transporting flumes to these remote sites; Keith Eshleman and Randy Richardson who spent days working alongside me in the blazing summer heat installing the stream gages; and Randy Richardson who was instrumental in digitizing over a hundred aerial photos. This research made use of data and models provided by: Aaron Friend acd Ben Cooper (Allegany County Soil Conservation District) ; Mike Kozier (Garret County Soil Conservation District); Jeff Griffith, Charles Strain, and Robert James (USGS); Dr. Ian Littlewood (Center for Ecology and Hydrology); the National Climat ic Data Center; and the Maryland Bureau of Mines. This research would not have been possible without the permission and cooperation of landowners Mr. & Mrs. Paul Willison and the late Simon Moore. Funding for this research was provided by a grant from the A.W. Mellon Foundation to promote collaboration via a collaborative eco logical research project between the Appalachian Laboratory and the Appalachian College Association. Ill TABLE OF CONTENTS List of Tables ................................................................................................................. v List of Figures ............................................................................................................... vi Chapter I: INTRODUCTION ............................................................. ...................... 1 A. Goals and Objectives .............................................................................. 6 Chapter II: METHODS ............................................................................................. 8 B. Study Sites .............................................................................................. 8 C. Field Hydrologic Measurements ........................................................... 13 D. Historical Hydrologic Measurements ................................................... 17 E. Unit Hydrograph Deconvolution .......................................................... 19 F. Historical Land Use/ Land Cover Derivation .. .................................... 20 G. Data Analysis ........................................................................................ 22 Chapter III: RESULTS ............................................................................................. 35 Chapter IV: DISCUSSION ....................................................................................... 61 Chapter V: CONCLUSIONS ................................................................................... 71 Appendix I. Coordinates of Watersheds and Gages ................................................. 73 Appendix II. LULC Classes, Codes, and Identification Key ..................................... 74 Appendix III. PC-IHACRES Model Results ............................................................... 7 5 Appendix IV. LULC Changes Over Time by Category (area in hectares) ................. 77 REFERENCES ............................................................................................................ 78 iv LIST OFTA BLES Table 1. Drainage area, slope, and elevation of watersheds used in comparative analysis ............................... ................................................... ... .................... 33 Table 2. Stage discharge relationships for the stream gages installed in the small catchment study ............................................................................................ 34 Table 3. Number of LULC patches, % of watershed, mean area, and total area in each LULC class for the Georges Creek watershed (1938-1997) ................ 60 V LIST OF FIGURES Figure 1. Generalized model of abstraction rates: -index and IHACRES .................. 23 Figure 2. Schematic representation of IHACRES ................................ ........................ 24 Figure 3. Site map and equipment locations for the small watersheds .. ..... ..... ............ .. 25 Figure 4. Watershed boundaries and 1997 LULC for Georges Creek and Savage River watersheds ........................................................................................... 26 Figure 5. Watershed slope: Georges Creek and Savage River ..................................... 27 Figure 6. Equipment installed at MAT 1 ....................................................... ................ 28 Figure 7. Plan and side views of flumes installed at MATl and NEFl ....................... 29 Figure 8. Plan and side views of stilling stream gage installed at EBNR ...... .......... ..... 30 Figure 9. Stage-discharge relationship for EBNR. ........................................................ 31 Figure 10. Schematic of double-ring infiltrometer ................................... ..................... 3 2 Figure 11. Average annual discharge and daily precipitation at MAT 1 and NEF 1. .... .43 Figure 12. Long-term average cumulative precipitation at Savage River Dam ...... ..... .44 Figure 13. Annual water balances for the small watersheds and larger basins ........... .45 Figure 14. Mean watershed response characteristics for MATl and NEFl.. ............... .46 Figure 15. Runoff coefficients and maximum rainfall intensities for MAT 1 and NEFl .............................................................................. ............................... 47 Figure 16. Total event runoff and maximum rainfall intensities for MAT 1 and NEFl ............. .. ....... ..... ..... ............... ... ................ .. .................. .................. ..... 48 Figure 17. Total rainfall vs total stormflow at MAT 1 and NEF 1.. ............................... .49 Figure 18. Peak runoff and maximum rainfall intensities for MAT 1 and NEF 1. ......... 50 Figure 19. Maximum rainfall intensity vs peak stormflow for MATl and NEFl. ....... 51 Figure 20. Unit hydrographs deconvolved for MATl and NEFl. ..... ..... ...................... 52 Figure 21. Cumulative depth of water infiltrated at MAT 1 and NEF 1. ............... ......... 53 vi Figure 22. Maximum hourly rainfall intensity vs soil infiltration capacities at MATl and NEFl .......................................................................................... 54 Figure 23. LULC change over time in the Georges Creek watershed (1938-1997) ...... 55 Figure 24. Primary LULC changes by percent in the Georges Creek Basin ................. 56 Figure 25. LULC changes by class in Georges Creek basin (1938-1997) .................... 57 Figure 26. Centroid lag and trend lines for the Georges Creek and Savage River watersheds (1952-2000) ............................................................................... 58 Figure 27. Runoff Ratios: George Creek vs Savage River .......................................... 59 vii Chapter I: INTRODUCTION The relationship between land use and land cover (LULC) and the hydrologic response of watersheds is becoming highly scrutinized in science, management, and public policy. In the majority of studies, the effects of deforestation, agriculture, urbanization, and wetland drainage have been examined. The watershed is frequently chosen as the basic unit of study for examining the effects of LULC change because watersheds have a definable hydrologic boundary; the area within the watershed boundary can be thought of as a "black box" where the difference between inputs and outputs are stored within the system. However, disturbance occurring within the system has the potential to alter the hydrologic responsiveness of watersheds (Freeze 1974). In the majority of studies of LULC change, hydrologic response characteristics such as changes in peak stormflow, flood frequency, and rainfall/runoff ratios have been examined. A number of studies have investigated the hydrological effects of timber harvesting (Hornbeck et al. 1970, Swift et al. 1975, Burt and Swank 1992, Jones and Grant 1996, Burton 1997, Kochenderfer et al. 1997, Thomas and Megahan 1998), urbanization and suburbanization ( Burges et al. 1998, Rose and Peters in press), and changes in agricultural areas and practices (Gebert and Krug 1996, Kuhnle et al. 1996, Allan et al. 1997, Mwendera and Mohamed-Saleem 1997). Changes in LULC often involve altering the land cover through intensive vegetation removal. Hornbeck et al. ( 1970), Burton ( 1997), and others have observed that intensive removal of vegetation can significantly increase runoff and flooding hazards. Most often, streamflow changes have been attributed to changes in evapotranspiration rates (Swift et al. 1975, Gifford et. al. 1984, Swanson 1984, Troendle and King 1987). Implementation of best management practices such as proper road design on logged lands can reduce the effects of timber harvesting (Kochenderfer et al. 1997, Thomas and Megahan 1998). In addition, Burt and Swank (1992) provide some evidence that as a forest regenerates it can exhibit evapotranspiration rates as high as dense grass. All of these studies suggest a strong relationship between land use change and watershed response, however. Another specific type of land use change that disturbs many of the physical properties of a watershed is the extraction of bituminous coal via surface mining. Surface mining and subsequent land reclamation has become widespread in the Appalachian region of the United States since the early 1950's (J. Carey, Maryland Bureau of Mines, personal communication) with the advent of large earthmovers. Under the Surface Mine Control and Reclamation Act of 1977 (SMCRA, PL 95-87) mine operators are obligated to reclaim surface mined lands to the approximate original contours and to acceptable LULC. The overall process involves extracting the material, or overburden, that overlies the coal seam. The topsoil is retained in a separate pile. Following coal extraction, the overburden is replaced, graded to the approximate original contour using large earthmovers, and typically seeded with grasses. A common result of reclamation is minesoils that are highly compacted (Bussler et al. 1984, Mcsweeney and Jansen 1984, Bell et al. 1994, Chong and Cowsert 1997). The Georges Creek watershed in western Maryland is an example of a watershed that has undergone intensive surface mining. Catastrophic flooding in the Georges Creek watershed in June of 1995 and January of 1996 led to speculation that surface mining and reclamation has altered the hydrologic response of the watershed and increased the 2 potential for damaging floods and associated economic losses. In addition to the economic losses caused by flooding, increased flooding frequency can have deleterious effects on stream biota. However, in the Georges Creek watershed as elsewhere, the effects of this LULC change on watershed stormflow response are poorly understood and empirical data on this phenomenon are essentially non-existent. A limited number of studies have investigated the hydrological effects of surface mining and reclamation on watershed stormflow response, but essentially no research has focused on the long-term cumulative impacts of mine reclamation distributed throughout a watershed. In theory, watersheds subjected to mine reclamation may respond similar to those having undergone urbanization/suburbanization, as both activities act to decrease the perviousness of the landscape. Most imperviousness on reclaimed surface mines is the result of massive compaction (Bussler et al. 1984, McSweeney and Jansen 1984, Bell et al. 1994, Chong and Cowsert 1997). Compaction has been shown to substantially reduce infiltration rates (Barnhisel and Hower 1997) and essentially eliminate the macropore networks (Dunker et al. 1995) that increase infiltration capacities (Beven and Germann 1982). Mine reclamation can also disturb water table elevations and subsurface flow paths (Bonta et al. 1992). Ritter and Gardner (1993) observed that on newly reclaimed mine lands in Pennsylvania, infiltration-excess overland flow is the dominant runoff process. Likewise Bonta et al. ( 1997) observed increased peak streamflow rates in response to rnjne reclamation. It could be argued that the limited data available for the pre-mining period, however, were insufficient to compare pre- and post-mining impacts. 3 The unit hydrograph technique is one method that could help quantify the effects of strip mine reclamation. The method was first outlined by Sherman (1932) and is still widely used in hydrological studies (Chapman 1996a, b, Dietrich 1996, Sefton and Boorman 1997), particularly in urban planning. The unit hydrograph of a watershed is defined as the hydrograph of one unit (inch or cm) of storm runoff generated by a rainstorm of uniform intensity and distribution occurring within a specific period of time (Dunne and Leopold 1978). Unit hydrographs are conducive to investigating hydrological effects of LULC change because in theory they are affected by a) rainfall characteristics and b) watershed characteristics. For small watersheds on the order of 1 km2 or less, many of the watershed characteristics are fixed from storm to storm (e.g., watershed area, topography, channel morphology, LULC, and soil properties). Therefore, one might expect that storms with similar rainfall characteristics (similar depth and intensity) would produce similar unit hydrographs. For larger watersheds on the order of 100 km2, however, the necessary assumption that a rain event is uniformly distributed over the watershed is usually difficult to achieve. Physiographic features, such as LULC, can change appreciably over relatively short time periods ( ~50 years). Based on unit hydrograph theory, if variations in rainfall characteristics can be minimized between watersheds and among the set of storms being analyzed, then differences in unit hydrograph shape could only be attributed to changes in physical watershed characteristics (e.g., LULC). Numerous methods exist for calculating unit hydrographs by deconvolution (Snyder 1938, Langbein 1940, Rantz 1971, US Soil Conservation Service 1972), one of which is the relatively simple - index method (Chow, et al. 1988) and IHACRES. Each of the models was based on basic unit hydro graph theory, although IHACRES uses a more sophisticated mathematical approach. However, satisfactory model fits could not be obtained when IHACRES was used to generate unit hydrographs for historical rainfall-runoff data from the larger Georges Creek and Savage River watersheds. The -index method was used for deconvolving unit hydrographs for the small watersheds for a thunderstorm that occurred on 6 August 2000 (this storm caused low- lying areas in the Georges Creek to be flooded). Based on the -index approach, unit 19 hydrographs were deconvolved assuming a constant rate of rainfall abstraction. Values for -index method (A) and non-linear decay used in IHACRES (B, from Littlewood et al. 1997). 23 .. Rainfall Effective rainfall Streamflow (mm/day) {mm/day) {mm/day) 10s ._,-_ -------~ . ,_ _ Ct,Nr.w.,,d ~lit u--:::1:~a~--------- ------l~n~:r~~:~~----t----__- __, : loss module .,____.__ function (Unit 1 ( ) Hydrograph) module ~ 3 parameters . I :_ ___________________ J----~~~~~~~:~ ______ 1 J 400 ,--------~ --To~lll --- TOIi! ...... ao,, - s. ... !S 10 1$ Air temperature Unit hydrographs Hydrograph separation (DC) (cumecs) {cumecs) Figure 2. Schematic representation of IHACRES used to deconvolve unit hydrographs at MAT l and NEF l adapted from Littlewood et al. ( 1997). 24 Figure 3. Locations of stream gages, watershed boundaries, permanent plots, and surface mined area (shaded) for the small watershed study located on Dans Mountain, Allegany County, Maryland. 25 N "'tE Savage River Georges Creek D Watershed Boundary 1997 Land Use Class 1 -o 1- 2 3- 4 6 Kilometers - Low intensity residential - High intensity residential -- - - Agriculture (hay1 1, asture/crop) - Forest (evergreen/deciduous/mixed) ,li''ii,,~ Active mine .Jili.=!~J - Reclaimed mine - Abandoned mine -a Spoil pile Landfill Quary - Water/wetland Figure 4. Locations, watershed boundaries, and 1997 LULC for the Georges Creek and Savage River watersheds, Allegany and Garrett Counties of western Maryland. 26 Georges Creek CJ Watershed Boundary Slope (degrees) CJ0 - 5 D 5 - 10 D 10 - 15 CJ 15 - 20 19 ? 20 1 0 1 2 3 4 5 Kilometers - 20 - 25 -25 - 30 - 30 - 35 - 35 - 40 - 40 - 45 Figure 5. Slope map of Georges Creek and Savage River watersheds, Allegany and Garrett Counties. 27 -- Figure 6. Equipment installed at MAT 1 for gaging watershed hydrologic inputs and outputs. Stream gage (Montana flume) is similar to that installed at NEFl. 28 -- . ???? . Throat width A B C D E l - ?---F 36 88-3/4 36 61-7/8 27 18 I 17 12 76-7/8 36 33-1/4 27 18 I 17 (A) A ? Channel bank Wing wall C Rip-rap area -, 1 rilling , \ ,w_ell ~ Channel bank ~ ..... D ~~ ... "" f~:?] ..\? : 6" X 6" timbers Backfill areas buried in channel bank --------------------------------------~--------------------------------------- (B) t Instrument F shelter L-.---.----J 1.? - = Flow ! . ' ! i : ..... ? ............. j . ~ i = Figure 7. Plan view (A) and side view (B) of Montana flumes installed at the MAT l and NEFl watersheds (dimensions in inches shown in accompanying table). 29 (A) Stream Channel 2" PVC Pipe 18" Galvanized Culvert (Stilling Well) (B) r-- Instrument Shelter .-> &Recorder Figure 8. Plan view (A) and side views (B) of stilling stream gage installed on the East Branch of Neff Run (EBNR) located on Dans Mountain, Allegany County, Maryland. 30 Arithmetic Axes 0.07 0.06 ? 0.05 ...,. -__ ' rJ:J 0.04 ~6 0 0.03 0.02 ? - __ y "':' ~l.454x4.3167 0.01 2 R =0.8838 0 0 0.05 0.1 0.15 0.2 0.25 Stage (m) Figure 9. Stage-discharge relationship for the gage installed on the East Branch of Neff Run (EBNR) during the period from 25 July 2000 to 1 October 2001. ' 31 Transparent Graduated Tube 30 cm diameter PVC Pipe 35 cmx 32 cmx 0.03 cm () Base Rests Plexi-glas Base (Top and Bottom) Atop Inner Ring of the ' Double-Ring ' lnfiltrometer Reservoir for double-ring infiltrometer RESERVOIR 1\ir Bubbles 0 0 Filler - - - - - Flow regulator for double-ring inJUtrometer Figure 10. Schematic of double-ring infiltrometer and water reservoir used to measure infiltration capacity (adapted from Eshleman 1985) 32 Table 1. Drainage area, slope, and elevation of watersheds used in comparative analysis. Area (km2) Sloee (degrees) Elevation (meters AMS) Min Max Mean Min Max Mean MATl 0.27 0 15 5 783 851 825 NEFl 0.03 6 13 10 689 778 727 EBNR 1.0 0 17 8 679 849 771 GCRK 186 0 36 10 302 911 658 SRIV 127 0 43 12 459 920 746 33 Table 2. Stage discharge relationships for the stream gages installed in the small catchment study. # Watershed Throat Width (in) Rating Curve 1. MATl 36 Q (cfs)= 12 H 1.5661 a 2. NEFI 12 Q (cfs)_- 4W H a c1.522 w II o.026J 3. EBNR NIA Qccms)=3 l .45 [H]4 3167 ? Q = discharge, Ha= head (depth) in feet, H = stage (height) in meters, W = flume throat width in feet. 34 Chapter III: RESULTS This study found a number of significant differences in the hydrological responses of watersheds subjected to LULC, specifically when comparing the surface mined and reclaimed watershed to one that was entirely forested. The small watersheds (MAT 1 and NEF 1) responded similarly on a water year basis, but varied in their response to individual rain events. Storms at MATl produced significantly greater runoff ratios, total runoff, and peak runoff than at NEF 1. Lag times for the two small watersheds were similar for the events analyzed in this study. However, at the river basin scale (Georges Creek and Savage River), watersheds varied from each other primarily in the timing of response to rainfall events. Despite widespread LULC change, other hydrological response characteristics (runoff ratios, peak runoff, total runoff) exhibited little difference at the river basin scale when compared between the two basins or within the basins over time. Annual hydrographs for water years 1 (2000) and 2 (2001) at MATl and NEFl can be found in Figure 11. Hydro graphs for the two water years of streamflow indicate that MAT 1 tends to produce higher, narrower peaks than NEF 1. For the majority of the water year, both watersheds responded primarily to major rain events and snow melts and produced little to no baseflow between rain events. However, during wetter months (e.g., April and May) NEFl produced some sustained baseflow between storms. Annual water balances ( l October to 30 September) for all sites as well as the normal year for Georges Creek and Savage River are shown in Figure 13. On an annual basis, each of the watersheds produced similar runoff yields, although MAT 1 tended to 35 produce more total runoff than NEF 1. Over the two years, roughly 26% of the rainfall input to the MAT 1 watershed leaves as surface runoff, compared to 25% at the NEF 1 watershed. Runoff yields varied slightly between years 1 and 2. MAT 1 produced similar annual runoff in both years, while NEFI decreased by 15%. Interestingly, this decrease at NEF 1 occurred despite an increase of 139 mm of precipitation in year 2 making it a wetter than normal year (Figure 12). Compared to long-term records for Georges Creek and Savage River, these estimates of annual yield are close to normal values (Figure 13) although the 2001 water year tended to be somewhat wetter than normal. ET yields were slightly higher at the small watersheds for both of the water years and also higher than the long-term averages. Long-term annual runoff yields for Georges Creek tend to be 100 mm less than the long-term average for Savage River Watershed. Statistically significant differences were observed between runoff coefficients and total event runoff produced at MAT 1 and NEF 1. Mean runoff coefficients for were calculated for the eight largest storms for which data exist at both gages (Figure 14). Runoff coefficients were significantly higher at MATI than at NEFI (p ~ 0.03), on average by as much as 2.5 times (Figure 15). Runoff coefficients at MAT 1 averaged 0.11 ranging from less than 0.01 to 0.26 (s.e. = 0.013) compared to NEFI where runoff coefficients averaged 0.04 ranging from no response to 0.13 (s.e. = 0.007). Runoff coefficients did not correlate with maximum rainfall intensity or total event rainfall (p ~ 0.05). The mean difference in total runoff (MATI - NEFI) for the eight largest storms where data exist for both gages was significantly greater than zero based on a one-tailed t-test. (p ~ 0.05). MAT 1 yielded roughly three times more total event flow than NEF 1 36 (Figure 16). Total event runoff at MATl averaged 5.0 mm per event and ranged from no response to 14 mm. Response at NEFl was significantly lower averaging 1.7 mm per event ranging from no response to 5.1 mm. This trend of greater total runoff at MAT 1 was observed in all but one of the storms, which occurred on 31 July 2000 (Figure 17). Total runoff at MAT 1 was significantly correlated to total event rainfall (r= 0. 794; p ~ 0.01; s.e. = 3.1; n= 10). Total rainfall explained 63% of the variation in runoff at MAT 1. At NEF 1 however, total rainfall explained less than 21 % of the variation in total runoff and a statistically significant relationship (r = 0.455; p ~ 0.05; s.e. = 1.8; n = 8) was not observed. Peak runoff rates for the eight storms investigated at MAT 1 were on average twice as large as those found for NEF 1, although the mean difference between the two watersheds was not significantly different from zero at the 0.05 level. Peak runoff rates at MAT 1 were consistently higher than at NEF 1, with the exception of one storm on 31 July 2001 (Figure 18). MATl averaged 1.0 mm/h (S.E. = 0.18) ranging from less than 0.1 mm/h response to 3.6 mm/h. On one occasion, peak runoff rates at MAT 1 reached 5.9 mm/h. Peak runoff rates at NEFl were lower, averaging 0.5 mmJh (s.e.= 0.09) and ranging from no response to 1.6 mm/h. Peak runoff rates at MAT 1 were significantly correlated with maximum rainfall intensity (r = 0.670; p ~ 0.05; S.E.= 1.5; n= 10), and a linear regression model explained 45% of the variation in peak stormflow (Figure 19). In comparison, peak runoff rates at NEFl were not significantly correlated with maximum rainfall intensities (r = 0.543; p ~ 0.05; s.e:.= 0.6; n=8), and a regression model only 30% of the total variation in peak stormflow. 37 Timing of runoff response at NEF 1 and MAT 1 was also calculated to compare the responsiveness of the watersheds to the accumulation of the rainfall pulses. For the eight storms compared in this study, the mean centroid lags (center of rainfall mass to center of runoff) based on hourly rainfall and runoff data for each watershed averaged 3 h, indicating no significant difference in the timing of response to rainfall. Two-hour unit hydrographs were deconvolved from rainfall and runoff observations for a thunderstorm occurring on 6 August 2000 using the -index method (Figure 20A). IHACRES was also used to deconvolve 1-hr unit hydrographs for the growing season (June to October) for both years 1 and 2 (Figure 20B). For the thunderstorm event, unit hydrograph shapes for each watershed were strikingly similar. MATl peaked slightly higher and receded more steeply than NEF 1. Similar results were obtained using IHACRES (see Appendix III for model fit parameters) when unit hydrographs were developed over the entire growing season. Similar to the 2-hr unitgraph for 6 August 2000, hydro graphs peaked slightly higher at MAT 1 than at NEF 1. Little change in unit hydrograph response was observed between year 1 and year 2. Unit hydrographs for both watersheds peaked approximately 0.1 mm higher in year 1 than in year 2. Soil infiltration capacity (or maximum infiltration rate assuming ponded water conditions) was also measured as an important variable influencing watershed stormflow response. As expected, steady-state infiltration capacities were lower at the reclaimed surface mine plots than on the forested reference watershed plots. This can be readily seen when examining the cumulative depth of water infiltrated at each plot (Figure 21). The point at which the curves become nearly linear provides an estimate of 38 the steady-state infiltration capacity of the soil. The reclaimed area at MAT 1 exhibited steady-state infiltration rates less than 1 cm/hr (n=3), or rates below the detection level of the infiltrometer. In contrast, soil infiltration experiments at NEF 1 yielded infiltration capacities that averaged nearly 30 cm/hr (n=2). For the 10 most intense storms at MAT 1 and NEF 1, soil infiltration capacities were exceeded in every case at MATl (Figure 21). However, at NEFl soil infiltration capacity was never exceeded by maximum hourly rainfall intensities. In addition to intensive measurements made for the two small watersheds, the physical and hydrological characteristics of Georges Creek and Savage River basins were also determined. During the last 60 years, the Georges Creek basin has undergone a wide range of LULC changes. Most change has occurred primarily within four LULC classes: surface mining, agriculture, forest, and development (Figure 23). Although some of these categories ( e.g., forests) have experienced minimal net change, others like agriculture and mining have undergone significant changes (Figure 24). Of most importance to this study are those LULC changes that have a direct effect on stream hydrology, such as those that alter evapotranspiration and imperviousness. LULC change statistics in the Georges Creek watershed for each time period are given in Table 3. Surface mining and reclamation in the Georges Creek watershed was one of the most visible and potentially the most influential factor on hydrology in the watershed (Figure 25A). Before the enactment of SMCRA in 1977, a limited number of surface mined lands underwent reclamation with a peak in surface mining and reclamation occurring 39 in the I 980's (John Camey, MD Bureau of Mines, personal communication). According to results obtained in this study, by 1982, 8.8% (1,649 ha) of the watershed had been surface mined and reclaimed. Total reclaimed area in the watershed has continued to increase such that by 1997 13% (2400 ha) of the watershed is reclaimed minesoils. Most of this land conversion came from two sources: agricultural lands and forestlands that were mined and reclaimed. In 1997, nearly 26 of the 105 mines in the watershed were within 50 m from surface waters, making stream channels highly susceptible to runoff produced from these adjacent mine lands. Active mining operations began in the late 1940's and peaked by the 1980's (Figure 25B). In 1962, active mining represented less than 1% of LULC in the watershed. Only 20 years later, active mining operations had increased by 700%. Available aerial photos show that surface mining peaked in 1982 with approximately 53 mines in active operation, representing nearly 3.5% of the total watershed LULC. Between 1938 and 1982, active surface mines were primarily located on lands that were previously agricultural land or had been forested. In 1997, most active mines were either previously forested, or were mines that were still in operation from 1962 or had been abandoned and re-mined (Figure 25C). Agricultural lands were one of several land uses that declined over the 60 yr period (Figure 25D). In 1938, 32% of the watershed was pastured, cropped, or planted as hayland. Over the next several decades, agricultural lands steadily declined. By 1997, less than 10% of the watershed was in active agriculture. Agricultural lands were primarily lost to surface mining or had been abandoned to re-generate as forestland. 40 Overall change in forested areas remained relatively low over the study period (Figure 25E). Nearly 65% of the Georges Creek watershed was covered in forests in 1938. Some forest regrowth occurred between 1938 and 1962 (74%), but was followed by a slight decrease through 1997 (70% ). Most forest regrowth occurred on abandoned agricultural lands. However, losses to surface mining and development offset any increases resulting in a net decrease in forest area. In 1997, a small area of strip mined land (4% of all forest lands) had returned to forest after mining. Overall development in Georges Creek on a per area basis, both commercial and residential, changed slightly from 1938 - 1997 (Figure 25F). The basin underwent a net increase in development of 2.2% (2.4 - 4.6). However, this represented approximately a doubling of developed area. Most of the change occurred in the low intensity residential category, which rose from 0.6 to 2.5%. The area of wetlands in the Georges Creek basin was found to be negligible. According to the National Wetlands Inventory (NWI), wetlands cover less than 1% of the basin. Little difference was observed in response characteristics on a storm-by-storm basis for 15 storms analyzed the Georges Creek and Savage River basin study. The primary diffei?ence in watershed response between the two basins was in the mean centroid lag. Georges Creek tended to respond on average three hours more quickly than Savage River (Figure 26). Mean runoff ratios for Georges Creek were significantly correlated to runoff ratios calculated for Savage River (Figure 27) (p ~ 0.001, r2 =0 .99, s.e. = 0.0139, n = 15). In addition the slope of the regression line was not significantly 41 different from 1 nor was the intercept significantly different from zero (p <0.05). No significant difference (p ~ 0.05) was observed in the mean peak runoff or runoff ratios for the Georges Creek and Savage River basins, even though Georges Creek often (73% of the time) produced higher peak runoff than the Savage River. Mean runoff ratios were essentially identical (GC = 0.068; SR= 0.075). In addition, there was no significant trend in runoff ratio, peak runoff, total runoff, or centroid lag when examined for each watershed over time (p ~ 0.05, n = 15). 42 ,,......, "7>, , ,-.._ 25 , "O C<:I "O 20 ~- - 40 s s s '--' s 15 '--' - Precipitation 60 ? ?.:::J <1.) --Matl ?sC<.:I. ~ C<:I 10 80 ..c: ?c:; .<,..,) <1.) Q 5 100 cl: o Il . t l :J ,J ?!~ JAt : .J ' l, , , n, : uv\/i, ~" . /lJL1 :. J :1 120 -.:?'?' -~~ ~P~ \.&:~ '<.t~ ov ov \#~"\, ~~"\, \.&:~"\, ..., P' \'?>-v "?--~ "?--~ ov Figure 11. Average annual discharge (normalized by area) and daily precipitation at MATI and NEFI from 1 October to 30 September 2001. 1200 ??r------- - ------- - - --------- -----~ c:::::::J Water Year 2000 c:::::::J Water Year 2001 1000 -+- Long-Term Average -????-?--?- ?? ? 800 ? 400 200 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Figure 12. Long-term average (1961-1990) cumulative precipitation observed at Savage River Dam station, Garret County, Maryland by water year. 44 Water Year Ending 2000 ? ET 1200 D Runoff 1000 - - - - - - ... 800 --"' :l> 425 :l> 564 .? 600 - 674 630 639 534 a ....___ ~ 400 '--- ,__ '-- .___ ~ 530 200 303 376 391 259 271 0 MAT! NEFI EBNR Georges Savage Georges Savage LT Creek River LT Watershed Water Year Ending 2001 1200 - - - 1000 - - - - - ... 800 - -"' 425 :l> 802 768 443 564 :l> .? 600 884 588 :::i '---.___ ~ 400 - - I--- - 200 - .___ 463 530 391 270 304 318 188 0 - MATl NEFI EBNR Georges Savage Georges Savage LT Creek River LT Watershed Figure 13. Annual water balances for the small watersheds and larger basins for water years ending 2000 and 2001 and long-term (LT) averages. 45 1.6 -.-----------...... 1.4 R~ 1.2 a 1.0 '-' ~ 0.8 - .. 0 i:::: ~ 0.6 ~ 0.4 Q) o... 0.2 0.0 -+--__.__-~- --.--'----'-~ TRIBMATI TRIB NEFI 6.0 ,,...__ 5.0 T ..~.... 1 , 4.0 - ~ g 3.0 ~ ca 2.0 T .L ~ 1.0 0.0 TRIBMATl TRIB NEFI 0.14 .... 0.12 T ?u~ 0.10 1 s Q) 0.08 8 0.06 ~ 0 T i:::: 0.04 J.. ~ 0.02 0.00 TRIBMATl TRIB NEFl Figure 14. Mean watershed response characteristics(? s.e.) for the eight most intense storms at the MAT l and NEFl watersheds between May and October 1999 to 2001. 46 0.40 0 -~ 0 0 0 0 0 --?[]--?-~- 0 0 0 0 .(."."..j .N... . ("] er, ..... - .~.... ~~..... N -gc...-.,. f.c..-.,. 0.35 - ..... ..... ~ ~ ."..'".. .'.C..i. N N ..--< ..--< in N00 00 00 ... .. .N... . ....-.-.<. .c.<..., .c..-.,. in s ..--< in '-0 ..... ..... - 20 ?' t- ?' '-0 t- 0.30 -- 40 ....... C ~ ?u 0.25 DMATl ~ ~ ? NEFl - 60 i 0 U 0.20 - D Max Hourly Rain lt:: - - 80 ~ 0 61 Total Rain C ?? ~ 0.15 - ~ 100 0.10 - - 120 0.05 - ~ - 140 0.00 -- ~Z,--L-'-=l,._L_ 1 2 3 4 5 6 7 8 9 10 StormRank Figure 15. Runoff coefficients and maximum rainfall intensities for the 10 most intense storms at the MAT 1 and NEF 1 watersheds between May and October 1999 to 2001. 47 - 0 0 0 0- 0 0 0 0 N N N -N- - N-- - N N ---- <") -I/-"-) --- --.. ..... \0 ?' t- -\0 ---- - 20 tw 40 ,,----.. ? DMATl ,,----.. ___, l5 - ? NEFl - 60 -' 1-, ..c:: ti:: 0 i:::: ? Maxlntens ~ ;:::::l '--' 0::: ? Total Rainfall 80 :::::::I ?fl lO - < ~ ::E 90 z ~ 0.30 50 % revegetation on reclaimed mines). Class 5: Active surface mines (areas currently being surface mined; visible coal seam, haul roads, and equipment). Class 6: Abandoned surface mines (open pits; often scattered shrubs in pits; no mining equipment visible). Class 7: Reclaimed surface mines (significant signs of recent reclamation; diversion ditches present; impressions in soil from reclamation equipment). Class 8: Spoil (primarily from deep mines; tailings, gob piles, deep mine openings). Class 9: Landfill (active landfilling; equipment and solid waste visible). 74 Appendix III. PC-IHACRES Model Results ====-===================----===========-------------- - - MATl 2000 IHACRES for WINDOWS, Version 1.02 FILE : D:\PROGRAMS\IHACRES\MATTHEW\M2000.SUM Date created :02/26/02 Time created :15:08:49 Record start date :01/06/2000 Record start time :01:00 Record end date :27/09/2000 Record end time :12:00 Record time interval 1 hourly Number of records 2844 results. CONTAINS : Summary of model Re f e rence Temperature = 20.00 8700 (2844), subints= l,Time Delay= Vers ion 1.02, Subperiod= 1,Range= 5857 to BO Const 1 Bias xl ul %ARPE T.C. Al f TauW %Run D -.529 .005 1.00 90 12.22 9.8 .o .04 1.57 ***** .005 1.00 90 12.22 .682 . 13 -.442 ***** .693 .19 1. 8 .o .05 1.23 1.00 90 12.22 . 0 .06 1.17 -.426 ***** .005 .5 .005 1.00 90 12.22 .694 .20 -.424 ***** .4 .o .06 1.17 .005 1.00 90 12.22 .694 . 20 . 0 .06 1.18 -.429 ***** .694 .19 1. 3 1.00 90 12.22 - --- - ---=======================--------------------------== MATl 2001 IHACRES for WINDOWS, Version 1.02 FILE : D:\PROGRAMS\IHACRES\MATTHEW\M2001.SUM Date created :02/26/02 Time created :15:23:27 Record start date :01/06/2001 Record start time :01:00 Record end date :25/09/2001 Record end time :01:00 Record time interval 1 hourly Number of records 2785 CONTAINS : Summary of model results. VReerfseiroenn c1e.0 2T,e mspuebrpaetruiorde== 12,R0a.0ng0e =14617 to17401(2785), subints= 1,Time Delay= Al BO Const 1 %Run Bias xl ul %ARPE T.C. f TauW D 1.00 1 Tw(tk) is less than 1 1.00 11 14.95 .007 .38 83.3 -.8 .02 2.09 -.619 ***** 1.00 11 14.95 .614 1.00 21 14.95 72.9 -.6 .02 1. 79 -.573 ***** .006 1.00 21 14 . 95 .692 .35 1.00 31 14.95 70.1 -.6 .02 1. 70 -.556 ***** .005 1.00 31 14.95 .720 .33 1.00 41 14.95 .005 14.95 .729 .31 69.5 -.6 .02 1. 67 -.550 ***** 1.00 41 1.00 51 14.95 .005 14.95 .730 .29 69.9 -.6 .02 1. 67 -.549 ***** 1.00 51 1.00 61 14.95 ***** .726 .27 70.7 -.6 .02 1. 68 - .551 1.00 61 14.95 .004 1.00 71 14.95 .02 1. 69 -.554 ***** -.6 1.00 71 14.95 .720 .24 71. 7 .004 1.00 81 14.95 .02 1. 71 -.558 ***** 1.00 81 14.95 . 713 .22 72. 9 -.6 .004 75 1.00 91 14.95 .02 1.74 -.563 ***** 1.00 14.95 .704 .20 74.1 -.6 91 .004 ==-----==-==============--~=-=---------==================== NEFl 2000 IHACRES for WINDOWS Version 1.02 FILE : D:\PROGRAMS\IHACRES\TRBNEF1\N200SUM.SUM D~te created :02/26/02 Time created :15:08:49 Record start date :01/06/2000 Record start time :01:00 Record end date :27/09/2000 Record end time :12:00 Record time interval 1 hourly Number of records 2844 CONTAINS : Summary of model results. Reference Temperature = 20 . 00 8689 (2833), Subi nts= l,Tirne Delay= to Version 1 . 02, Subperiod= 1,Range= 5857 1 T.C. Al BO Const f Tauw %Run D Bias xl ul %ARPE 1.00 61 108.94 . 0 .04 1. 58 -.531 3.400 .050 1.00 61 108.94 .664 .14 10.6 ------==----=================--=-=======-=----------------- NEFl 2001 IHACRES for WINDOWS, Version 1.02 Date created :02/26/02 Time created :15:19:35 Record start date :01/06/2001 Record start time :01:00 Record end date :27/09/2001 Record end time :01:00 Record time interval 1 hourly Number of records : 2833 FILE D:\PROGRAMS\IHACRES\TRBNEF1\N2001.SUM CONTAINS : Summary of model results. Reference Temperature = 20.00 to17449(2833), Subints= l,Tirne Version 1. 02, Subperiod= 1,Range=14617 Delay= 1 1/c Tq Ts Vs f TauW %Run D Bias xl ul %ARPE 1.00 60 9.97 .1 . 0 .06 341. 5 .81 27.28 .458 1.00 60 9.97 .755 .01 1.00 61 9.97 343.4 .81 27.26 .458 1.00 61 9.97 .755 .01 .1 .0 .06 76 Appendix IV. LULC changes over time by category (area in hectares) 1962 LID HID AG FOR ACTMIN ABANMIN RECMIN SPOIL LFIL SUM LID 64.0 0.8 18.0 24.8 0.0 0.3 0.0 0.0 0.0 108 HID 25.2 261.1 26.5 30.1 0.0 0.0 0.0 0.2 0.0 343 AG 57.6 47.7 QC) 2998.1 2549.2 25.3 279.1 0.0 32.4 0.0 5990 ~ ~.... FOR 12.8 1.4 556.9 11214.4 77.3 340.5 0.0 62.2 0.0 12265 ACTMlN 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ABANMIN 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SPOIL 0.1 1.4 3.9 42.1 0.3 0.2 0.0 22.2 0.0 70 SUM 160 312 3603 13861 103 620 0 117 0 18776 1982 LID HID AG FOR ACTMIN ABANMlN RECMIN SPOIL LFIL SUM LID 87 .0 18.3 12.4 39.9 0.0 0.0 0.0 0.0 0.0 158 HID 11.7 260.8 16.7 22.5 0.0 0.0 0.0 0.0 0.0 312 -.J C: -.J N AG 131.4 34.5 1583.8 1283.8 165.8 12.5 387.4 5.4 0.0 3605 zc \0 ~.... FOR 62.7 17.5 639.6 11619.3 371.8 78.0 1053.8 18.1 0.0 13861 :) ~ ACTMlN 0.0 0.0 1.7 48.4 11.6 7.7 33.4 0.1 0.0 103 C, ABANMIN 1.1 0.0 34.9 264.1 98.1 60.9 161.6 0.0 0.0 621 SPOIL 2.4 0.1 3.9 77.1 3.8 4.8 12.3 12.6 0.0 117 ;; SUM 296 331 2293 13355 651 164 1649 36 0 18775 '" 1997 LID HID AG FOR ACTMIN ABANMIN RECMlN SPOIL LFILL SUM LID 174.4 34.8 26.9 58.2 0.2 0.0 1.7 0.0 0 .0 296 HID 47.7 259.6 4.0 19.6 0.0 0.1 0.1 0.0 0.0 331 AG 70.3 45.5 1222.3 736.6 39.6 5.0 173.3 0.4 0.0 2293 N 00 FOR 170.5 63.0 397.3 11563.4 185.6 68.0 862.7 12.5 31.2 13354 ~.... ACTMlN 0.7 0.0 33.8 140.4 75.7 1.8 398.5 0.4 0.0 651 ABANMIN 0.3 0.0 3.5 92.1 0.0 10.6 57.1 0.3 0.0 164 RECMIN 0.3 0.1 99.0 532.4 97.9 18.0 898.6 2.1 0.0 1648 SPOIL 0.1 0.1 5.0 18.5 0.0 1.3 7.5 3.7 0.0 36 SUM 464 403 1792 13161 399 105 2400 19 31 18774 REFERENCES Allan, J.D., Erickson, D.L., and J. Fay. 1997. The influences of watershed landuse on stream integrity across multiple spatial scales. Freshwater Biol. 37:149-161. 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