runoff
Hydrologic Modeling of Land Processes in Puerto Rico Using Remotely Sensed Data
Sat, 07/30/2011 - 13:02 — ckassHydrologic Modeling of Land Processes in Puerto Rico Using Remotely Sensed Data
Cruise, J. F.; Miller, R. L.
Journal of the American Water Resources Association, vol. 30, Issue 3, p.419-428
Abstract:
An integrated, multi-disciplinary effort to model land processes affecting Mayaguez Bay in western Puerto Rico is described. A modeling strategy was developed to take advantage of remotely sensed data. The spatial, interannual, and seasonal variability of sediment discharges to the bay were also evaluated. Classified images of remotely sensed data revealed the spatial distribution and quantities of land use classes in the region and aided in the discretization of the watershed into homogeneous regions. These regions were modeled using a geomorphic modeling technique based upon spatially averaged parameters.
Simulation results from the modeling effort compared favorably with observations at two locations within the watershed. Results showed that runoff and sediment loads from the area exhibit a marked seasonal trend and that deforested areas located in the foothill regions of the watershed contribute a disproportionate share of the sediment load to the bay. In years when rainfall distributions are uniformly distributed over the area, the sediment yields may be up to 100 percent higher than years when the rainfall is concentrated in the heavily forested mountainous regions.
Luquillo Mountains Puerto Rico A water energy and biogeochemical budgets program site
Tue, 07/26/2011 - 16:52 — ckassLarsen MC, Stallard RF. Luquillo Mountains, Puerto Rico–a water,
energy, and biogeochemical budgets program site. US geological
survey fact sheet. Washington, D.C.7 U.S. Geological
Survey; 2000. p. 163– 99.
Abstract:
The Puerto Rico research site consists of the 113 square-kilometer Luquillo
Experimental Forest (LEF), administered by the U.S. Forest Service, and
the nearby Río Grande de Loíza drainage basin, an urbanized and agriculturally-
developed watershed. This combined region serves as a terrestrial
laboratory for the study of issues related to the global loss of tropical
forest, and the associated changes in land-use practices. Findings from
the WEBB research help scientists understand how vegetation, landscape,
and people interact to affect the quantity and quality of water and the
erosion of the landscape. The results of this work can be applied not only
to Puerto Rico, but also to many other regions, where deforestation and
rapid land-use change are issues.
WATER BUDGETS OF FORESTED AND AGRICULTURALLY-DEVELOPED WATERSHEDS IN PUERTO RICO
Tue, 07/26/2011 - 16:40 — ckassWATER BUDGETS OF FORESTED AND AGRICULTURALLY-DEVELOPED WATERSHEDS IN PUERTO RICO
Abstract:
Accurate assessment of water budgets is critical for effective management of water resources,
especially on small, densely-populated islands with extremely limited storage capacity such as
Puerto Rico. A water budget defines a balance between inputs, outputs, and storage. The water
budgets described herein provide a generalized summary of the inputs, extractions, and outputs
from four watersheds in and near the Luquillo mountains using rainfall, runoff, and public-supply
extraction data as well as estimates of groundwater losses and inputs such as cloud drip and
infiltration from septic tanks. Mean annual rainfall accumulation during a 7-year study (1991 to
1997) ranged from 1,722 mm in the Canóvanas watershed, to 4,235 mm in the Icacos and
Mameyes watersheds; the Cayaguás watershed had 2,172 mm. Combined runoff, groundwater
flow and withdrawals ranged from 47 to 73 percent of inputs (combined rainfall, cloud drip and
septic tank infiltration). Evapotranspiration, calculated as the water budget residual, amounted to
27, 40, 44, and 53 percent of total moisture inputs in the Icacos, Cayaguás, Mameyes, and
Canóvanas watersheds, respectively.
Unusual Hydrograph Characteristics, Upper Río Chagres, Panamá
Sat, 07/23/2011 - 21:24 — ckassJustin M Niedzialek, "Unusual hydrograph characteristics, upper Rio Chagres, Panama" (January 1, 2007). Dissertations Collection for University of Connecticut. Paper AAI3265788.
Abstract:
Inaccessible locations and inhospitable working conditions have resulted in a lack of detailed hydrological knowledge in the tropics. I have established a new field observatory located near the town of Gamboa, Panama, adjacent to the mid-point of the Panama Canal. This observatory allowed detailed measurements of the hydrologic cycle at the first-order catchment scale. My investigations reveal that competing runoff production mechanisms are responsible for the observed streamflow. Both of these mechanisms are strongly dependent upon rainfall rate and secondarily upon cumulative rainfall volume. I have identified a small but hydrologically significant riparian zone that is decoupled from the hillslope. In contrast to the remainder of the catchment this riparian zone shows signs of frequent overland flow. Upslope regions occasionally produce overland flow during high-intensity rainfall. Parallel to the small scale studies in Gamboa, sub-watersheds of the 414 km2 upper Rio Chagres were instrumented. These gages showed that the Rio Chagres rarely reacts uniformly; instead, the observed runoff is usually the result of a limited portion of the watershed. Based on inspiration from field research a new conceptual model, Sac3, was developed. Sac3 was successfully calibrated and verified on several study watersheds. Sac3 was also used to explore the relationship deep groundwater storages had on seasonal changes in baseflow runoff behavior.
Stormflow generation in a small rain-forest catchment in the Luquillo Experimental Forest, Puerto Rico
Fri, 07/22/2011 - 14:29 — ckassSchellekens,J.; Scatena, F. N.; Bruijnzee, L.A.; van Dijk, A. I. J. M.; Groen, M. M. A.; van Hogezand, R. J. P. 2004. Stormflow generation in a small rainforest catchment in the Luquillo Experimental Forest, Puerto Rico.. Hydrol. Process. 18, 505-530.
Abstract:
Various complementary techniques were used to investigate the stormflow generating processes in a small headwater catchment in northeastern Puerto Rico. Over 100 samples were taken of soil matrix water, macropore flow, streamflow and precipitation, mainly during two storms of contrasting magnitude, for the analysis of calcium, magnesium, silicon, potassium, sodium and chloride. These were combined with hydrometric information on streamflow, return flow, precipitation, throughfall and soil moisture to distinguish water following different flow paths. Geo-electric sounding was used to survey the subsurface structure of the catchment, revealing a weathering front that coincided with the elevation of the stream channel instead of running parallel to surface topography. The hydrometric data were used in combination with soil physical data, a one-dimensional soil water model (VAMPS) and a three-component chemical mass-balance mixing model to describe the stormflow response of the catchment. It is inferred that most stormflow travelled through macropores in the top 20 cm of the soil profile. During a large event, saturation overland flow also accounted for a considerable portion of the stormflow, although it was not possible to quantify the associated volume fully. Although the mass-balance mixing model approach gave valuable information about the various flow paths within the catchment, it was not possible to distill the full picture from the model alone; additional hydrometric and soil physical evidence was needed to aid in the interpretation of the model results
