Rating curves have been used to relate suspended sediment concentrations as a function of discharge. This study developed suspended sediment rating curves by combining data from the United States Geological Survey and Long-term Ecological Research databases for the following nine rivers in eastern Puerto Rico: Quebrada 1, Quebrada 2, Quebrada 3, Quebrada Sonadora, Quebrada Guaba, Rio Icacos, Rio Mameyes (Puente Roto), Rio Mameyes at Rt. 3 and Rio Fajardo. Using a 95-percent

confidence interval discharge accounted for 22.5, 13.6, 25.7, 34.9, 41.2, 53.9, 30.5, 31.7, and 62.6 percent of the suspended sediment concentration variation respectively. When comparing rivers outside of the Luquillo Experimental Forest, the Rio Mameyes at Rt. 3 and Rio Fajardo, to the other seven rivers located within the Luquillo Experimental Forest, there was no significant difference in the concentration of suspended sediment per unit of discharge. Therefore, according to the results of this

study the land use practices within the drainage basins of the Rio Mameyes at Rt. 3 and the Rio Fajardo do not significantly increase the concentration of suspended sediment per unit of discharge.

Suspended Sediment Dynamics in Mountain Streams of Puerto Rico

Suspended SedimentNatural vs. Development

Suspended Sediment as a pollutant

Ecological and Economic costs

Total Suspended Sediment (TSS) vs. Suspended Sediment Concentration (SSC)

Biocomplexity ProjectRivers and Roads

ObjectivesDevelop suspended sediment rating curves for the following nine streams: Quebrada 1, Quebrada 2, Quebrada 3, Quebrada Sonadora, Quebrada Guaba, Rio Icacos, Rio Mameyes (Puente Roto), Rio Mameyes at Rt. 3 and Rio Fajardo.

Compare SS rating curves for rivers within the Luquillo Experimental Forest (LEF) to those outside of the LEF.

HypothesesTSS will be positively correlated to a river’s discharge and will best be described by a power function.

Rivers outside of the LEF, Rio Mameyes at Rt. 3 and Rio Fajardo, will have greater concentrations of TSS per unit of discharge compared to the other seven sites within the LEF.

Study Sites

Elevation range (m)

Area (km2) Forest types Bedrock

LTER Sites El Verde watersheds Quebrada Sonadora (QS) 350-1050 2.65 Tabonuco, Colorado, Dwarf and Palm Volcanoclastic Rio Icacos watershed Quebrada Guaba (QG) 750-900 0.3108 Colorado Grandiorite Rio Icacos (RI) 600-800 3.263 Colorado Grandiorite Bisley watersheds Quebrada 1 (Q1) 260-415 0.067 Tabonuco Volcanoclastic Quebrada 2 (Q2) 267-465 0.0634 Tabonuco Volcanoclastic Quebrada 3 (Q3) 265-665 0.35 Tabonuco and Palm Volcanoclastic Mameyes Puente Roto (MPR) 100-1050 17.52 Tabonuco, Colorado, Dwarf and Palm Volcanoclastic Non-LTER Sites Mameyes Mameyes at Rt. 3 (M3) 0-1050 34.71 Forest, Agricultural and Developed Volcanoclastic Rio Fajardo Rio Fajardo (RF) 0-1050 38.59 Forest, Agricultural and Developed Volcanoclastic

Rio Mameyes at Rt. 3 (outside LEF)

TSS mg/L = aQb

With 95% confidence

Sites

Sample Max TSS

(mg/L)

Sample Min TSS

(mg/L)

Sample Median

TSS (mg/L)

Sample Max Q

(mm/day)

Sample Min Q

(mm/day)

Sample Median Q (mm/day) a b r2

Q1 1292 1.14 18.6 175.2 0.04 2.09 1.201 0.392 0.225 Q2 1510 1.24 8.37 177.1 0.04 2.30 0.857 0.367 0.136 Q3 840.0 1.06 5.20 109.6 0.26 3.69 0.473 0.500 0.257

M3 920.3 1.01 3.15 50.69 0.71 3.07 0.098 1.072 0.317

MPR 2148 1.01 3.10 704.4 0.14 5.98 0.022 0.702 0.305

QG 753.5 1.45 6.99 33.33 1.3 2.59 0.233 1.480 0.417

QS 187.2 1.01 2.30 67.47 0.02 1.97 0.306 0.491 0.349

RI 289.7 1.05 2.69 429.3 2.4 7.80 -0.399 1.110 0.539

RF 6700 2.00 39.0 430.5 0.28 4.31 0.853 1.020 0.626

ConclusionsFor the nine study streams total suspended solids can be expressed as a power function of discharge.Using a 95-percent confidence interval discharge accounts for 22.5, 13.6, 25.7, 34.9, 41.2, 53.9, 30.5, 31.7, and 62.6 percent of the TSS variation for the following rivers: Quebrada 1, Quebrada 2, Quebrada 3, Quebrada Sonadora, Quebrada Guaba, Rio Icacos, Rio Mameyes (Puente Roto), Rio Mameyes at Rt. 3 and Rio Fajardo respectively.Rio Mameyes at Rt. 3 and Rio Fajardo, both sites outside of the Luquillo Experimental Forest, did not have significantly higher concentrations of suspended sediment per unit of discharge when compared to the other seven rivers located within the Luquillo Experimental Forest.

AcknowledgementsThe author expresses her gratitude to Dr. Fredrick Scatena and Dr. Ellen Wohl for their guidance and support throughout the REU program. In addition, this project could not have been conducted without the wealth of data that individuals have collected for the USGS and LTER databases. Funding for the REU Program in Water Research at CSU was provided by a grant from the The DoD's ASSURE (Awards to Stimulate and Support Undergraduate Research Experiences) Program in partnership with the National Science Foundation.

Results

Site Characteristics

Quebrada Sonadora (within LEF)

Research Experiences For Undergraduates - Program in Water Research at Colorado State University - Summer 2006

Discharge in mm of runoff/day

Tota

l Susp

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olid

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g/L

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Outside the LEF

Arica CrootofFaculty Mentors: Ellen Wohl and Frederick Scatena

Suspended Sediment Rating Curves For the Nine Study Streams

Suspended Sediment Rating Curve for Quebrada Sonadora

Discharge (mm of runoff/day) Discharge (mm of runoff/day)

Tota

l Susp

ended S

olid

s (m

g/L

)

Tota

l Susp

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olid

s (m

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Suspended Sediment Rating Curve for Mameyes at Rt. 3

Puerto RicoFourth largest Caribbean island

Subtropical maritime climate

Receives ~1,600mm of precipitation each year

Discharges 2.7-9.0 million metric tonnes of suspended sediment each year

Luquillo Experimental Forest

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