Sources and pathways of ground-water flow to canyon streams as ...

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Sources and pathways of ground-water flow to canyon streams as ...

Outline• Study sites:– Lower Las Garzas and Pine Creeks• Proposed model of ground-water inputs• Methods of analysis:– Streamflow recession analysis– Stream surveys– Longitudinal measurements of specific conductance• Incorporating watershed disturbances• Implications for mitigation monitoring


Stream Characteristics• Deep granitic canyon with broad, flat,sedimentary ridge-tops• Channel morphology—step-pool or canyon poolrifflearchitecture• Intermittent stream with some perennially flowingreaches• Alternating reaches of thick and thin cobble/boulder alluvium overlying granitic bedrock• For Las Garzas, pools are relatively free ofsediment due to dam upstream


Digital elevation model—lower Las Garzas CreekCarmel RiverLower Las Garzas CreekBroad tributary uplandsSource: USGS National Elevation Dataset


Aquifer Characteristics• Fractured-granitic, deep (regional) zone:consistent low-flow source related topermeability of discrete fractures• Shallow (local) zone: limited higher-dischargingsource responding to antecedent rainfallpatterns and carry-over from wet years• Alluvial channel water: storage and mixing ofremnant wet-season runoff and accretion flowsources


Streamflow Records• Compare baseflow recession patterns(flow persistance) from year to year


0192219241926192819301932193419361938194019422004194419461948195019521954195619581960196219641966196819701972197419761978198019821984198619881990199219941996199820002002504540353025201510583 Year Mean Rainfall = 21.31Water YearAnnual rainfall at San Clemente Dam and 3-year moving average.Observer: California American Water Company.Source: Monterey Peninsula Water Management DistrictAnnual Rainfall (inches)


25-Sep18-Sep11-Sep4-Sep28-Aug21-Aug14-Aug7-AugPine Creek- 1995 - 199731-Jul24-Jul17-Jul10-Jul3-Jul26-Jun19-Jun12-Jun5-Jun29-May22-May15-May8-May1-May1010.10.011995 (36.3 inches, 170% of mean)1996 (22.4 inches, 105% of mean)1997 (21.7 inches, 102% of mean)Flow (cfs)


Pine Creek - 1995 - 2002101Flow (cfs)0.11995 (36.3 inches, 170% of mean)1996 (22.4 inches, 105% of mean)1997 (21.7 inches, 102% of mean)1998 (46.3 inches, 217% of mean)1999 (17.4 inches, 82% of mean)2000 (20.4 inches, 96% of mean)2001 (21.0 inches, 99% of mean)2002 (15.6 inches, 73% of mean)0.0125-Sep18-Sep11-Sep4-Sep28-Aug21-Aug14-Aug7-Aug31-Jul24-Jul17-Jul10-Jul3-Jul26-Jun19-Jun12-Jun5-Jun29-May22-May15-May8-May1-May


25-Sep18-Sep11-Sep4-Sep28-Aug21-Aug14-Aug7-AugPine Creek - 1998 - 200431-Jul24-Jul17-Jul10-Jul3-Jul26-Jun19-Jun12-Jun5-Jun29-May22-May15-May8-May1-May1010.10.011998 (46.3 inches, 217% of mean)1999 (17.4 inches, 82% of mean)2000 (20.4 inches, 96% of mean)2001 (21.0 inches, 99% of mean)2002 (15.6 inches, 73% of mean)2003 (24.3 inches, 114% of mean)2004 (18.1 inches, 85% of mean)Flow (cfs)


Baseflow Surveys• Delineate the extent of flowing reaches,isolated pools and dry segments at varioustimes of the dry-down• Track the progression of stream dry-down


©2004 Balance Hydrologics, Inc.


©2004 Balance Hydrologics, Inc.


©2004 Balance Hydrologics, Inc.


Water quality monitoring• Measure specific conductance to identifydistinct ground-water sources and tracktrends stream profile• Provides a metric to use that isindependent of sediment filling and easierto measure at ultra-low flow conditions


1300Specific Conductance (umhos/cm @ 25 C)120011001000900800700600500400300MPWMD Gage at West Garzas RoadMPWMD Gage near Garzas CanyonRedwood CynSpring at mouth ofRedwood Cyn.(2002)Snivleys Ridge TribVasquez Knob NW TribPinyon Peak TribSLP Property LineVasquez Knob GulchLot 212 TribVasquez Knob West TribLong Ridge NW TribSLC Gage at Moore's Lake OutflowJune 6, 2002SLC Gage at Moore's Lake Inflow2001000Alluvial FanReachTerraced Alluvial Reach(pool-riffle)Pinyon Peak Reach(step-pool)Lower SLP Reach(pool-riffle)Upper SLP Reach(step-pool)BelowMoore's Lake0 5000 10000 15000 20000 25000Distance from Carmel River (feet)Moore'sLakeFigure 2.Specific conductance measurements in Lower Las Garzas Creek, 1990, 1991, 2002, 2003,and 2004, Monterey County, California. For 2002, 2003, and 2004, breaks in trend lines indicate thatflow was zero at some point between the two measurements. The 1990 and 1991 surveys did not cover theupper reaches of the canyon. 2003 measurements by Rob Thompson (SLC); other surveys by BalanceHydrologics staff.


1300Specific Conductance (umhos/cm @ 25 C)120011001000900800700600500400300MPWMD Gage at West Garzas RoadMPWMD Gage near Garzas CanyonRedwood CynSpring at mouth ofRedwood Cyn.(2002)Snivleys Ridge TribVasquez Knob NW TribPinyon Peak TribSLP Property LineVasquez Knob GulchSeep above bedrockfalls (9/02)Lot 212 TribVasquez Knob West TribLong Ridge NW TribSLC Gage at Moore's Lake OutflowSeptember 23, 2002July 31, 2002June 6, 2002SLC Gage at Moore's Lake Inflow2001000Alluvial FanReachTerraced Alluvial Reach(pool-riffle)Pinyon Peak Reach(step-pool)Lower SLP Reach(pool-riffle)Upper SLP Reach(step-pool)BelowMoore's Lake0 5000 10000 15000 20000 25000Distance from Carmel River (feet)Moore'sLakeFigure 2.Specific conductance measurements in Lower Las Garzas Creek, 1990, 1991, 2002, 2003,and 2004, Monterey County, California. For 2002, 2003, and 2004, breaks in trend lines indicate thatflow was zero at some point between the two measurements. The 1990 and 1991 surveys did not cover theupper reaches of the canyon. 2003 measurements by Rob Thompson (SLC); other surveys by BalanceHydrologics staff.


1300Specific Conductance (umhos/cm @ 25 C)120011001000900800700600500400300MPWMD Gage at West Garzas RoadMPWMD Gage near Garzas CanyonRedwood CynSpring at mouth ofRedwood Cyn.(2002)Snivleys Ridge TribVasquez Knob NW TribPinyon Peak TribSLP Property LineVasquez Knob GulchSeep above bedrockfalls (9/02)Lot 212 TribVasquez Knob West TribLong Ridge NW TribSLC Gage at Moore's Lake OutflowSeptember 23, 2002July 31, 2002June 6, 2002August 23, 1991October 30, 1990SLC Gage at Moore's Lake Inflow2001000Alluvial FanReachTerraced Alluvial Reach(pool-riffle)Pinyon Peak Reach(step-pool)Lower SLP Reach(pool-riffle)Upper SLP Reach(step-pool)BelowMoore's Lake0 5000 10000 15000 20000 25000Distance from Carmel River (feet)Moore'sLakeFigure 2.Specific conductance measurements in Lower Las Garzas Creek, 1990, 1991, 2002, 2003,and 2004, Monterey County, California. For 2002, 2003, and 2004, breaks in trend lines indicate thatflow was zero at some point between the two measurements. The 1990 and 1991 surveys did not cover theupper reaches of the canyon. 2003 measurements by Rob Thompson (SLC); other surveys by BalanceHydrologics staff.


Natural watershed disturbancesaltering baseflow• Wildfire• Episodic high-flow events• Pool-sediment infilling/scour


Summary• The shallow aquifer system, especially in theside canyons, is an important source of carryoverbaseflow following wet years– Streamflow recession analysis and stream surveys• The deep aquifer supports summer flows in thedeepest portion of the canyon, in the driest timesof the year, and during very dry years– Specific conductance


Conclusions• In this case, the need for careful description ofhydrogeologic connection to streamflow is drivenby habitat considerations, not for the morecommon searches for water, movement ofcontaminants, or locations to store contaminants.• Monitoring-based mitigation through multiple linesof evidence is more effective than flow-thresholdor reference-year comparison-based mitigation inlow-flow and intermittent streams, and moreadaptive to future watershed changes


©2004 Balance Hydrologics, Inc.


©2004 Balance Hydrologics, Inc.


1300Specific Conductance (umhos/cm @ 25 C)120011001000900800700600500400300MPWMD Gage at West Garzas RoadMPWMD Gage near Garzas CanyonRedwood CynSpring at mouth ofRedwood Cyn.(2002)Snivleys Ridge TribVasquez Knob NW TribPinyon Peak TribSLP Property LineVasquez Knob GulchLot 212 TribVasquez Knob West TribLong Ridge NW TribSLC Gage at Moore's Lake OutflowJuly 31, 2002June 6, 2002SLC Gage at Moore's Lake Inflow2001000Alluvial FanReachTerraced Alluvial Reach(pool-riffle)Pinyon Peak Reach(step-pool)Lower SLP Reach(pool-riffle)Upper SLP Reach(step-pool)BelowMoore's Lake0 5000 10000 15000 20000 25000Distance from Carmel River (feet)Moore'sLakeFigure 2.Specific conductance measurements in Lower Las Garzas Creek, 1990, 1991, 2002, 2003,and 2004, Monterey County, California. For 2002, 2003, and 2004, breaks in trend lines indicate thatflow was zero at some point between the two measurements. The 1990 and 1991 surveys did not cover theupper reaches of the canyon. 2003 measurements by Rob Thompson (SLC); other surveys by BalanceHydrologics staff.


Ground-water factors affectingbaseflow in intermittent coastalCalifornia streams– Annual recharge from the prior wet season– Time since last major recharge event (streampersistence carry-over)– Distance downstream of a major tributary,fracture zone or seep– Contribution from deepest aquifer storage(generally insensitive to recent recharge)– Depth-to-bedrock beneath stream

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