PREDICTION OF MASTER RECESSION CURVES AND BASEFLOW RECESSIONS IN THE LUQUILLO MOUNTAINS OF PUERTO RICO¹

Abstract

An analysis of hydrograph recessions and rainfall data was performed to estimate the recession constants for two watersheds in the Luquillo mountains of Puerto Rico. To account for seasonal rainfall patterns, the data were grouped into dry and wet seasons. Sets of three Master Recession Curves (MRC) per season for each watershed were developed: one using the Matching Strip Method (MS) and two using variations of the Correlation Method (CM). These variations were the envelope line (CME) and the least squares regression (CMR). Other regression based analytical expressions that consider the streamflow recession as an autore‐gressive or an integrated moving average process were also applied. The regression based methods performed consistently better than the graphical ones and they proved to be faster, easier, and less subjective. The recession constants from these methods were then used to estimate the time it would take the streamflow to reach the critical Q99 flow duration. Based on this study, once the streamflow reaches Q90, water managers have 6 to 12 days warning before streamflow reaches critical levels.

Applicability Assessment of Estimation Methods for Baseflow Recession Constants in Small Forest Catchments

“…White and Sloto [18] explained the point where direct runoff ends as a function of catchment area. In some cases, two days from the time of peak flow occurrence were excluded in the analysis because direct runoff is considered to be dominant during those periods [9]. Arnold et al [12] and Cheng et al [6] excluded two days from the time of peak flow occurrence for normal rainfall events and five days for heavy rainfall events.…”

“…Until the early 20th century, graphical techniques, such as the matching strip method and correlation method, were widely used for recession analysis [9]. They were used to find the master recession curves that could be representative of the various recession properties affected by many factors [8].…”

“…Sujono et al [11] noted that several recession constants are obtained when using the matching strip method. Negative opinions of this method have been expressed, but some researchers have simultaneously argued that more precise estimations of the recession constants can be derived from the researcher's own judgment [9,11].…”

“…Based on the hydraulic theory about recession characteristics, several analytical approaches have also been presented to derive the recession constants [6,13]. These methods are based on the least-square method, and several previous studies have proposed these methods to be a better tool for recession analysis [6,9,13,14].…”

“…Simultaneously, validation tests of each method are also being studied [15]. In addition, several studies have examined the applicability of these methods [9,11]. However, most of these studies were carried out in relatively large catchments with areas that are larger than 100 ha, with few applications in small forest catchments.…”