Abstract
The overall goal of this report was to understand river discharge variability to improve conventional water management practices of Mexico’s northern subtropical rivers. This report addresses whether: a) river discharge tendencies, patterns and cycles can be detected with proxy and instrumental records; and b) annual discharge can be forecasted by stochastic models. Eleven gauging stations of six major rivers; three lowland rivers discharging into the Pacific Ocean (Rios Santa Cruz, Acaponeta, and San Pedro); five upland rivers draining into the Pacific Ocean (Rio San Pedro: Pena del Aguila, Refugio Salcido, San Felipe, Vicente Guerrero and Saltito), one river flowing across the interior Basin (Rio Nazas: Salome Acosta) and two more rivers discharging into the Northern Gulf of Mexico (Rio San Juan: El Cuchillo and Rio Ramos: Pablillos) were statistically analyzed. Instrumental recorded daily discharge data (1940-1999) and reconstructed time series data (1860-1940) using dendrochronological analysis delivered annual discharge data to be modeled using autoregressive integrated moving average, ARIMA models. Spectral density analysis, autocorrelation functions and the standardized annual discharge data evaluated annual discharge frequency cycles. Results showed ARIMA models with two autoregressive and one moving average coefficient adequately project river discharge for all gauging stations with four of them showing significant declining patterns since 1860. ARIMA models in combination with autocorrelation and spectral density techniques as well as standardized departures, in agreement with present (2002-2010) observations, forecast a wet episode that may last between 9 and 12 years thereafter entering again into a dry episode. Three dry-wet spell cycles with different time scales (1-2 years; 4-7 years; 9-12 years) could be discerned from these analyses that are consistent for all three northern Mexico’s river clusters that emerged from a multivariate analysis test.
Highlights
Mexicos freshwater availability is high with an average of 474.9 Km3 year-1 that equates to 4,749 m3 inhabitant-1 year-1 (México, 2005)
Two previous discharge values are well related to the present discharge and the time series has on the average one cycle
This research shows that variability of river discharge could be detected in proxy and instrumental discharge records as well as that ARIMA models with a linear tendency predicted well the reconstructed and instrumental time series data
Summary
Mexicos freshwater availability is high with an average of 474.9 Km3 year-1 that equates to 4,749 m3 inhabitant-1 year-1 (México, 2005). Overall only 18% of water resources are pumped out from rivers and aquifers for consumptive use, totaling 78,000 M m3 y-1. This volume supplies agriculture (78%), urban-public (12%), industry (8%), and livestock (2%) (México, 2001). Mexico’s irrigated area total 6.3 M ha, of which 3.4 M ha are irrigated with surface water and the remaining 2.9 M ha with primarily groundwater (México, 2005). Per capita water availability is steadily declining since it was close to 18,000 m3 inhabitant-1 year-1 in the 1950’s (México, 2007). Several over-stressed regions by persistent shortages have water pressure indices well above 100%
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