Mark A. Gonzalez National Riparian Service Team

1. Three Novellas: Past, Present and Future Conditions of the San Pedro Riparian National Conservation Area Mark A. Gonzalez National Riparian Service Team

2. Outline Past, Present and Future Conditions of the San Pedro Riparian System Novella 1: Once Upon a Time – Holocene history of the SPRNCA Novella 2: Flower Power – Everything you needed to know about plants but were afraid to ask Novella 3: Making a Better Sponge – Processes that store and release water along the San Pedro River

3. INTRODUCTION Project Area San Pedro Riparian National Conservation Area International border to St. David SPRNCA boundary (from Hereford 1993)

4. Novella I: Once upon a Time – Holocene History of the SPRNCA

5. Holocene Setting Piedmont/Fan Inner Valley Basin Fill Basement Rock

6. Holocene Setting Inner Valley Pre-entrenchment Landforms Entrenchment Landforms

7. Holocene Setting Weik Ranch Mbr. 6500-4300 yrs BP (Qwk) Hargis Ranch Mbr. 3500-2000 yrs BP (Qha) McCool Ranch Mbr. 2000 BP to AD 1880 (Qmc) Teviston alluvium (Qtv) Little Ice Age (AD 1450-1850) paleosol Qwk Qmc-B Qha Qmc-B Qmc-A Qmc-A 4000 yrs BP 7500 yrs BP 2600 yrs BP Historic 1900 yrs BP Sources: Haynes 1987; Hereford 1993; Waters and Haynes 2001

8. Holocene Setting: McCool Ranch paleosol ¼ mi S of Boquillas Wash ¼ mi N of Casa de San Pedro 1 mi S Summers Wells Garden Wash Boquillas Wash Qtv Qtv Qtv Qtv Qtv Qmc Qmc Qmc Qmc Qmc

9. Holocene Setting: McCool Ranch paleosol • Physical Conditions • Little Ice Age (AD 1450-1880) • Low-energy environment • Shallow depth to water table • High organic-matter content (esp. from paleo-cienega) • Water storage and release patterns Qtv Qmc

10. Pre-entrenchment Conditions • Biological Conditions • Widespread cienega formation • Herbaceous dominated communities

11. Period of Entrenchment Timing (1880s-1910s +/-, Hereford 1993) • Downstream initiation (1882, Contention area) • Upstream migration (1908 – Hereford Bridge) • Spread into and up tributary drainages San Pedro River Pre-entrenchment channel: Shallow Post-entrenchment channel: Deep

12. Channel Evolutionary Sequence • t1 Stable channel • t2 Downcutting • t3 Widening • t4 Aggradation t2 t1 stable t3 widening t1 t3 t2 downcutting t4 aggradation

13. Summary • Stream valleys evolved naturally throughout the Holocene Period in response to climatic fluctuations. • Aggradation (valley filling) coincident with wet/cool periods and high water tables • Channel incision and sediment removal coincident with dry/warm periods Qwk Qmc-B Qha Qmc-B Qmc-A Qmc-A Sources: Haynes 1987; Hereford 1993; Waters and Haynes 2001

14. Summary Channel Evolutionary Sequence: SPR in ‘infancy’ • t1 Stable channel • t2 Downcutting • t3 Widening • t4 Aggradation t2 t1 stable t3 widening t1 t3 t2 downcutting t4 aggradation

15. Novella II:Flower Power --Everything you ever wanted to know about plants but were afraid to ask

16. Past –Plant Communities Channel + Terrace Floodplain/Cienega • Perennial Flow • Obligate wetland plants: Hardstem and threesquare bulrush; flatsedge; cattail,

17. Past –Plant Communities Channel Terrace Floodplain/Cienega • Perennial (water-table < 20 ft depth) • FACW plants: Sacaton; bunchgrass/shrub; mesquite (+/- dependent on fire regime)

18. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Perennial Reaches Obligate, and facultative wetland species: hardstem and threesquare bulrush; cattail; spikerush; horsetail, and seepwillow

19. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Intermittent Reaches Johnsongrass, Bermudagrass, seepwillow, and minor occurrences of hydric herbaceous species

20. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Perennial Reaches Fremont cottonwood / Goodding’s willow; Baccharis, with lesser amounts of netleaf hackberry, mulberry, grama grasses

21. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Intermittent Reaches Fremont cottonwood / Goodding’s willow; xeric woody shrub (AZ ash and walnut, hackberry) with tamarisk/; baccharis and herbaceous understory

22. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Perennial Reaches Sacaton – Mesquite continuum Sacaton dominated with frequent fire Mesquite dominated with fire suppression

23. Present – Plant Communities Holocene Terraces Channel Terrace Floodplain Intermittent Reaches Increase in woody shrubs and decrease in herbaceous plants Facultative plants more common than hydric plants

24. Summary Holocene Terraces • Plants in and near the riparian zone ‘stratify’ themselves by: • Depth to water • Permanence / seasonality of water (i.e., Perennial vs. Intermittent flow) Channel Terrace Floodplain

25. Novella III:Making a better sponge – storing and releasing water

26. Water Storage: Banks I Standard Form II Ponded Form III Tributary Fan Form IV Adjustment Form (I) (IV) (I) (III) (II)

27. Water Storage: Banks When stage (water level) is high in the channel, water is forced (pushed by hydrostatic pressure) into the banks and stored in the floodplain alluvium. When stage falls in the channel, the hydraulic gradient is reversed and water flows out of the banks and into the channel to supply baseflow between high-flow events

28. Water Storage: Banks Ponded water moves out of channel and into banks during high stage. Stored water also moves down valley with the hydraulic gradient. (I) (IV) (I) (III) (II)

29. Water Storage: Floodplain Floodplain recharge has greater surface area than channel-bank recharge alone. This permits more water to enter alluvial aquifer in short time.

30. Water Storage: Floodplain Roughness To increase floodplain infiltration, Floodplain vegetation must decrease water velocity

31. Vegetation Response Grazing closure in 1988 (< 25 years ago) has allowed riparian vegetation to establish and grow. View from Hereford Bridge: (left) circa mid-1980s (BLM); (right) 10 years later (photos by D. Krueper, BLM)

32. Water Storage: Trapped Sediment

33. Water Storage: Trapped Sediment and organic matter

35. Water Holding Capacity of Soil Organic Matter 195 lbs H2O 200 160 140 lbs H2O 120 100 lbs H2O Pounds H2O in 100 Pounds of Soil 80 55 lbs H2O 40 33 lbs H2O 1 5 2 4 3 Percent Organic Matter (modified from Carpenter)

36. Loss of water storage West East 4200 ft Inner Valley Pre-entrenchment alluvium V.E. = 100X 4100 ft Available water volume in SPRNCA pre-entrenchment alluvial aquifer (WVa) composed of silt loam: WVa= (448 acres/mile X 40 miles) X 20 ft thickness X 1.7”/ft÷ (12”/ft) WVa= 50,000 acre-feet Pre-entrenchment alluvial aquifer (with 3’ thick cienega soil on 3600 acres (1/5 of riparian area) and MODEST 5% organic matter): WVa= 50,000 acre-ft + (16,000 gallons X 5 X 3’ X 3600 acres) ÷ (325,851 gals./acre-ft) WVa= 50,000 acre-ft + 2650 acre-ft = 52,650 acre-ft 0 0.5 1 1.5 km Miles 1 0.5

37. Loss in water storage West 4200 ft East Inner Valley Post-entrenchment alluvium V.E. = 100X 4100 ft Available water volume in SPRNCA for post-entrenchment alluvial aquifer (WVa) composed of sand: WVa= (128 acres/mile X 40 miles) X 10 ft thickness X 0.9”/ft÷ (12”/ft) WVa= 3840 acre-feet 0 0.5 1 1.5 km Miles 1 0.5

38. Controls on Perennial Flow St David 14 Escalante 13 St David 12 Smrs-Cnt’n 11 Tombstone 10 Depot Reaches 9-10 Predominantly Intermittent Reaches 1-8 Predominantly Perennial Hwy 82 9 Fairbank 8 Boquillas Babocomari R. 7 Charleston 6 Escapule 5 Lewis Spr. Hwy 90 4 Cottonwood 3 Hunter 2 Hereford- Kolbe Hwy 92 1 Palominas

40. 14 • Reaches 1-4 Perennial: • Underlain by restrictive silt-clay layers • Reaches 5-8 Perennial: • Gaining reaches with water upwelling on the east side of the silt-clay restrictive layer • Reaches 9-14 Intermittent: • Bedrock controlled or smaller basin contributions 13 12 11 10 9 8 7 6 5 4 3 2 1 USA AZ MEX SN

41. East 7500 West 6000 Elevation, ft above sea level 4000 2000 3 miles

42. South North Palominas Charleston gage Hereford Cottonwood Lewis Spring Boquillas Fairbank 4000 Elevation (ftamsl) 3000 3 Miles

43. Summary: Change in water Storage West East Post-entrenchment alluvium 4200 ft Inner Valley V.E. = 100X 4100 ft Pre-entrenchment estimated available water storage: 50,000 acre-ft Post-entrenchment estimated available water storage: 4000 acre-ft 0 0.5 1 1.5 km Miles 1 0.5

44. Summary Bigger sponges store more water--Sponges get bigger as: • Vegetation covers riparian area • Vegetation slows stream velocity and enhances infiltration • Vegetation / organic matter is trapped in sediment Bottom Line: More vegetation = more water storage

45. Summary Bigger sponges store more water--Sponges get bigger as: • Sediment accumulates and aggrades on floodplain • Floodplain widens • Floodplains are inundated • Tributary mouth fans (and beaver) pond water Bottom line: More deposition = more water storage

46. Summary Continued improvement in riparian conditions is dependent upon seasonal timing of streamflow, adequate runoff volume and sediment load, and unrestrained floods. Factors that reduce runoff volume, increase salinity, change runoff seasonality, or reduce sediment loads are detrimental to the riparian community (Hereford, 1993). Protection of both the flow and the sediment regime of this river are crucial to its survival.