Discharge records from the gaging stations in the Mississippi Basin are available online from the U.S. Geological Survey (USGS ) for the early 1900's to the present (http://water.usgs.gov/usa/nwis/sw/). Older records for some stations are available back into the early 1800's from the U.S. Mississippi River Commission (1955). We compared the online and printed data where they overlapped and found the digital and printed records to be identical.
Discharge records from gaging stations on the Rio Grande in New Mexico are available online from the USGS (http://water.usgs.gov/usa/nwis/sw/). Data on Rio Grande gaging station measurements in Texas are available from the International Boundary and Water Commission (http://www.ibwc.state.gov/).
We used mean annual discharge (sum of mean daily flow for year divided by days in calendar year) in cubic feet per second (cfs) in our study to minimize the impacts of dams and other human modifications of river flow on the records. Location and date of construction for dams and locks along rivers shown in the following figures are from the National Atlas (http://www.nationalatlas.gov/).
Discharge records were compared with a composite record of ENSO events shown in figure 4 that we compiled from a variety of sources. The events under NOAA in figure 4 are major events since 1950 as identified by the National Oceanic and Atmospheric Administration multivariate ENSO index. Data are from NOAA's Climate Diagnostics Center (http://www.cdc.noaa.gov/ENSO/enso.kd.html).
Events under CPC in figure 4 are from NOAA's Climate Prediction Center. The CPC data are a seasonal assessment of El Niño and La Niña conditions based on sea-surface-temperature (SST) conditions in the tropical Pacific Ocean since 1950 (see
http://www.cpc.noaa.gov:80/products/analysis_monitoring/ensostuff/ensoyears.html). We used the CPC seasonal characterizations to identify significant El Niño and La Niña events. Years with El Niño or La Niña conditions in all four seasons were classified as an El Niño or La Niña event as appropriate. In general, years with moderate or strong El Niño or La Niña designations in two or more seasons were identified as events if the seasons were adjacent. The year of the event was based on the likely effects of the event. Table 1 shows the CPC data and our identification of El Niño and La Niña years.
http://www.cpc.noaa.gov:80/products/analysis_monitoring/ensostuff/ensoyears.html). We used the CPC seasonal characterizations to identify significant El Niño and La Niña events. Years with El Niño or La Niña conditions in all four seasons were classified as an El Niño or La Niña event as appropriate. In general, years with moderate or strong El Niño or La Niña designations in two or more seasons were identified as events if the seasons were adjacent. The year of the event was based on the likely effects of the event. Table 1 shows the CPC data and our identification of El Niño and La Niña years.
Events under JMA+1 in figure 4 are based on SST anomalies in the tropical Pacific as determined by the Japan Meteorological Agency since 1914. The index uses 5-month running means of spatially averaged SST anomalies over the area between lats 4°S.-4°N. and longs 180°W.-90°W. Anomalies must exceed threshold values of ±0.5 for 6 months to be classified as the warm or cold phase of ENSO. The ENSO events tabulated by the JMA are in water years (October to September). We have added 1 year to the JMA dates because events starting in October tend to affect extratropical areas in the following calendar year (see http://www.coaps.fsu.edu/~legler/jma_index.html).
Events under DK+1 in figure 4 are from Diaz and Kiladis (1992). ENSO events are identified by a combination of changes in the Southern Oscillation Index (SOI) and tropical SST anomalies derived from ship data since 1877 (see Kiladis and Diaz, 1989). The ENSO events listed in Diaz and Kiladis (1992) are in water years (October to September), and so we have added 1 year to the events to translate them into calendar years.
Events under Z in figure 4 are derived from plots of the SOI and SST changes since 1886 in the eastern equatorial Pacific region known as NINO3 (see Zebiak, 1999, fig. 2). We designate El Niño and La Niña events for years in which the plot shows that both the SOI and NINO3 indices deviate >±1 from average values. The composite record used in our study is listed under the heading PDDW (Poore, Darling, Dowsett, Wright) in figure 4.
We used several standard statistical techniques to compare flow records with ENSO events and to compare variance in the flow records with the SOI. The Mann-Whitney U-test was used to determine if ENSO extremes (El Niño versus La Niña) were associated with significantly increased or decreased river flow. Details and explanation of the technique are in Mann and Whitney (1947) and Tamhane and Dunlop (2000). To further explore the relation between ENSO and flow in the Rio Grande, we performed a cross-spectral analysis on flow data and the SOI by using the Blackman-Tukey method (Jenkins and Watts, 1968) between 1915 and 1997 for the Embudo record and between 1930 and 1997 for the Presidio record. To make the SOI comparable with our data, we converted the monthly SOI index (see
http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/FTP_SITE/INT_DIS/readmes/soi.html) to an annual mean (sum of monthly SOI index divided by months in calendar year)
http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/FTP_SITE/INT_DIS/readmes/soi.html) to an annual mean (sum of monthly SOI index divided by months in calendar year)
U.S. Geological Survey, U.S. Department of the Interior
This page is https://pubs.usgs.gov/bulletin/b2187/data.html
Contact: Harry Dowsett (hdowsett@usgs.gov)
Last modified 09.07.01 (krw)
This page is https://pubs.usgs.gov/bulletin/b2187/data.html
Contact: Harry Dowsett (hdowsett@usgs.gov)
Last modified 09.07.01 (krw)