Table 1: Tropical cyclones during ENSO and baseline years. 



Table 2 lists the anomalies calculated. It is noted that the baseline months included the effects on precipitation 

 from four tropical cyclones. Additionally, because proportions developed use counts of months rather than 

 precipitation amounts, extreme events cannot excessively and unreahsticaUy skew results. The results reveal a 

 mixture with El Nino monthly precipitation ranging from a (positive) 1.3 percent anomaly in the BeeviUe 5 NE 

 data to a -30.7 percent anomaly in the Corpus Christi data. La Niiia anomalies ranged from -12.7 to 25.9 

 percent, also a mixed result. Four of six ENSO anomahes were negative. Both ENSO phases led to negative 

 anomalies at the Corpus Christi gauge, but a smaller anomaly (-12.7 percent) for La Nina months that included 

 the effects from 8 tropical cyclones. The inland gauge, Sabinal, yielded the same pattern of a more positive 

 anomaly from La Nina months, but this pattern was not maintained in the Beeville 5 NE data. NX'hile the 

 Beeville 5 NE and Corpus Christi WSO AP gauges yielded the same anomaly for La Nifia months, there was a 

 large difference in the El Nino related anomaly despite being separated by only about 40 miles (however, 

 Beeville 5 NE is inland about 35 miles). There is a "weak" sviggestion that ENSO events may lead to a 

 somewhat higher proportion of negative anomalies than expected by randomness (discounting the zero 

 anomaly, there is a 23 percent probability of obtaining 4 negative anomahes in 6 possibihties). More data from 

 additional gauges would be needed to further explore this possibility. Generally, these analyses in search of a 

 precipitation dependence on ENSO do not reveal any well-defined pattern, but rather expressed the high 

 variability in the precipitation data. 



Table 2: Percentage anomaly of monthly ENSO rainfall when compared to base year 75 percentile 

 benchmark precipitation. 



Beeville 5 NE 

 La Nina: -12.7% 

 El Nino: +1.3% 



Sabinal 

 La Nina: 

 El Nino: 



+25.9% 

 -6.8% 



Corpus Christi 

 La Nina: -12.7% 

 El Nino: -30.7% 



DAILY PRECIPITATION DISTRIBUTION COMPARISONS 



While there appears litde indication of a trend in the annual and monthly precipitation of the Nueces River 

 watershed during the 1940 to 1999 period, there remained the possibility that there could have been a 

 difference in the distribution of daily precipitation across the three periods of interest in the Rincon Project 

 study. For example, the mean monthly precipitation during the second period could have been similar to that 



D-8 ^* Recent Trends in Precipitation Occurring on the Nueces River Watershed of South Texas 



