Hydrology

Helping HELP with limited resources: the Luquillo experience

Scatena, F.N.; Ortiz-Zayas, JR; Blanco-Libreros, J.F. 2008. Helping HELP with limited resources: the Luquillo experience. Water SA. 34(4 special HELP edition): 497-508.

Abstract: 
By definition the HELP approach involves the active participation of individuals from a wide range of disciplines and backgrounds, including representatives of industry, academics, natural resource managers, and local officials and community leaders. While there is considerable enthusiasm and support for the integrated HELP approach, a central problem for all HELP basins is how to effectively engage individuals and groups with few, if any financial resources. In the Luquillo HELP project we have managed this issue by focusing our efforts on holding small, public meetings and workshops with technocrats and managers who are engaged in local water resource management. To date several forums have been organised, including: technical meetings with the directors of natural resource agencies; presentations and panel discussions at the meetings of local professional societies, including the societies of Civil Engineers and Architects, the Commonwealth Association of Tourism, the Association of Builders and Developers, and the Puerto Rican Association of Lawyers. During these forums HELP specialists gave presentations and led discussions on how integrated watershed management can help resolve local problems. Because the audience are directly involved with these issues, they are quite responsive to these discussions and have often provided unique solutions to common problems. Technical workshops are co-sponsored by local municipalities – these day-long workshops are hosted by a municipality and include managers from other municipalities, the local water authority, and local community leaders. Additional activities include: technical advice on water infrastructure projects is given; there are educational exchanges between local and international students, scientists, natural resource managers, and community leaders; and synthesis publications relevant to integrated water resource management are produced. Other activities have included compiling oral environmental histories and organising watershed restoration activities. This paper describes these activities and discusses the benefits and costs of each approach.

The HELP (Hydrology for the Environment, Life and Policy) Experience in North America

Abstract: 
inking water, and that almost 2.5 billion have no access to proper sanitation.” Many in the international water community stress the importance of integrated water-resources management (IWRM) to address these challenges. They argue that this is the most effective means of sustaining economic and social welfare while protecting the health of vital ecosystems. One reaction to this call for more effective management has been the Hydrology for the Environment, Life and Policy initiative, or HELP1. HELP has created a framework that enables water-law and policy experts, water-resources managers, and scientists to work together on water-related problems. HELP is a joint initiative of UNESCO and the World Meteorological Organization (WMO). Its primary goals are to: • establish a global network of HELP basins with operational links between research scientists and policymakers; • direct hydrological science toward integrated basin policy and management; • provide opportunities to learn lessons from other basins; and, • promote social and economic well-being of stakeholders via sustainable use of water as an ecological resource. With these goals, scientists, managers, policy experts, and other stakeholders within HELP watersheds address locally defined water-related issues, including water and climate; water and food; water quality and human health; water and environment; and water and conflict.

Wet canopy evaporation from a Puerto Rican lower montane rain forest: the importance of realistically estimated aerodynamic conductance

Abstract: 
Rainfall interception (I) was measured in 20 m tall Puerto Rican tropical forest with 4 complex topography for a one-year period using totalizing throughfall (TF) and stemflow 5 (SF) gauges that were measured every 23 days. Measured values were then compared to 6 evaporation under saturated canopy conditions (E) determined with the Penman-Monteith 7 (P-M) equation, using (i) measured (eddy covariance) and (ii) calculated (as a function of 8 forest height and wind speed) values for the aerodynamic conductance to momentum flux 9 (ga,M). E was also derived using the energy balance equation and the sensible heat flux 10 measured by a sonic anemometer (Hs). I per sampling occasion was strongly correlated with rainfall (P): I = 0.21P + 0.60 (mm), r2 11 = 0.82, n = 121. Values for canopy storage 12 capacity (S = 0.37 mm) and the average relative evaporation rate (E/R = 0.20) were 13 derived from data for single events (n = 51). Application of the Gash analytical 14 interception model to 70 multiple-storm sampling events using the above values for S and 15 E/R gave excellent agreement with measured I. For E/R = 0.20 and an average rainfall intensity (R) of 3.16 mm h-1, the TF-based E was 0.63 mm h-116 , about four times the value derived with the P-M equation using a conventionally calculated ga,M (0.16 mm h-117 ). 18 Estimating ga,M using wind data from a nearby but more exposed site yielded a value of E (0.40 mm h-119 ) that was much closer to the observed rate, whereas E derived using the energy balance equation and Hs was very low (0.13 mm h-120 ), presumably because Hs was 21 underestimated due to the use of too short a flux-averaging period (5-min). The best 22 agreement with the observed E was obtained when using the measured ga,M in the P-M equation (0.58 mm h-123 ). The present results show that in areas with complex topography, 1 strongly underestimated when calculated using 2 equations that were derived originally for use in flat terrain; hence, direct measurement of ga,M using eddy covariance is recommended. The currently measured ga,M (0.31 m s-13 ) 4 was at least several times, and up to one order of magnitude higher than values reported for forests in areas with flat or gentle topography (0.03–0.08 m s-15 , at wind speeds of about 1 m s-16 ). The importance of ga,M at the study site suggests a negative, downward, 7 sensible heat flux sustains the observed high evaporation rates during rainfall. More work 8 is needed to better quantify Hs during rainfall in tropical forests with complex 9 topography.

Comparison of passive fog gages for determining fog duration and fog interception by a Puerto Rican elfin cloud forest

Holwerda, F.; Bruijnzeel, L.A.; Scatena, F.N. 2010. Comparison of passive fog gages for determining fog duration and fog interception by a Puerto Rican elfin cloud forest. Bruijnzeel, L.A.; Scatena, F.N.; Hamilton, L.S., eds. Tropical Montane Cloud Forests: Science for Conservation and Management. Cambridge, UK: Cambridge University Press. p. 275-281.

Abstract: 
Rates and amounts of fog interception by vegetation depend on wind speed, fog liquid water 4 content (LWC) and duration, as well as surface area and geometry of the vegetation 5 (Schemenauer, 1986). Information on the timing and duration of fog can be obtained with 6 passive fog gages, provided these are protected from rainfall and equipped with a recording 7 device (Bruijnzeel et al., 2005). Fog LWC may also be evaluated from collections by passive 8 gages when information on their collection efficiency and prevailing wind speeds is available 9 (e.g. Schemenauer and Joe, 1989). A variety of passive gages is available, and there has been 10 some discussion as to what is the most suitable type of gage to characterize local fog 11 conditions (Juvik and Nullet, 1995a; Schemenauer and Cereceda, 1995; cf. Delay and 12 Giambelluca, in press; Frumau et al., this issue). For example, a cylindrical gage is considered 13 superior to a flat screen, because it has uniform exposure to all wind directions (Juvik and 14 Nullet, 1995a; cf. García Santos and Bruijnzeel, this issue; Giambelluca et al., this issue). On 15 the other hand, a flat screen generally has a much larger collection area than a cylindrical 16 gage, and may thus measure fog when LWC or wind speeds are low (Schemenauer and 17 Cereceda, 1995).

Characteristics of fog and fogwater fluxes in a Puerto Rican elfin cloud forest

Eugster, Werner ; Burkard, Reto; Holwerda, Friso; Scatena, Frederick N.; Bruijnzeel, L.A.(Sampurno) 2006. Characteristics of fog and fogwater fluxes in a Puerto Rican elfin cloud forest.. Agricultural and Forest Meteorology 139 :288-306.

Abstract: 
The Luquillo Mountains of northeastern Puerto Rico harbours important fractions of tropical montane cloud forests. Although it is well known that the frequent occurrence of dense fog is a common climatic characteristic of cloud forests around the world, it is poorly understood how fog processes shape and influence these ecosystems. Our study focuses on the physical characteristics of fog and quantifies the fogwater input to elfin cloud forest using direct eddy covariance net flux measurements during a 43-day period in 2002.We used an ultrasonic anemometer–thermometer in combination with a size-resolving cloud droplet spectrometer capable of providing number counts in 40 droplet size classes at a rate of 12.5 times per second. Fog occurred during 85% of the time, and dense fog with a visibility <200 m persisted during 74% of the period. Fog droplet size depended linearly on liquid water content(r2 ¼ 0:89) with a volume-weighted mean diameter of 13.8 mm. Due to the high frequency of occurrence of fog the total fogwater deposition measured with the eddy covariance method and corrected for condensation and advection effects in the persistent upslope air flow, averaged 4.36 mm day1, rainfall during the same period was 28 mm day1. Thus, our estimates of the contribution of fogwater to the hydrological budget of elfin cloud forests is considerable and higher than in any other location for which comparable data exist but still not a very large component in the hydrological budget. For estimating fogwater fluxes for locations without detailed information about fog droplet distributions we provide simple empirical relationships using visibility data.

Linking habitat stability to floods and droughts: effects on shrimp in montane streams, Puerto Rico

COVICH, A. P., T. A. CROWL, AND F. N. SCATENA. 2000. Linking
habitat stability to floods and droughts: effects on
shrimp in montane streams, Puerto Rico. Verhandlungen
der Internationalen Vereinigung fu¨ r theorestische und
angewandte Limnologie 27:2430–2434.

Abstract: 
Most previous studies on Caribbean flood and drought frequency have examined hydrological (e.g. MORRIS & VAZQUEZ 1990, GARCIA et al. 1996) rather than ecological effects (COVICH et al. 1998). We analyzed temporal and spatial distributions of rainfall, stream flow, and mean maximum pool depth over an 8-year period (1990–1997) to evaluate effects of variable flows. We examined the response of a biotic variable (the coefficient of variation in shrimp densities) to changes in water depth (coefficient of variation of maximum pool depth) along an elevational gradient.

Drinking Water from Forests and Grasslands: A Synthesis of the Scientific Literature

Dissmeyer, George E.; [Editor] 2000. Drinking water from forests and grasslands: a synthesis of the scientific literature. Gen. Tech. Rep. SRS-39. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 246 p

Abstract: 
This report reviews the scientific literature about the potential of common forest and grassland management to introduce contaminants of concern to human health into public drinking water sources.Effects of managing water, urbanization, ecreation, roads, timber, fire, pesticides, grazing, wildlife and fish habitat, and mineral, oil, and gas resources on public drinking water source quality are reviewed.Gaps in knowledge and research needs are indicated. Managers of national forests and grasslands and similar lands in other ownerships,environmental regulators,and citizens interested in drinking water may use this report for assessing contamination risks associated with land uses.

Water Withdrawn From the Luquillo Experimental Forest, 2004

Crook, Kelly E.; Scatena, Fred N.; Pringle, Catherine M. 2007. Water Withdrawn From the Luquillo Experimental Forest, 2004. U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry. Gen. Tech. Rep. IITF-GTR-34.

Abstract: 
This study quantifies the amount of water withdrawn from the Luqillo Experimental Forest (LEF) in 2004. Spatially averaged mean monthly water budgets were generated for watersheds draining the LEF by combining long-term data from various government agencies with estimated extraction data. Results suggest that, on a typical day, 70 percent of water generated within the forest is diverted before reaching the ocean. This is up from an estimated 54 percent in 1994. Analysis showed that up to 63 percent of average monthly stream runoff is diverted from individual watersheds during drier months. Watersheds with large water intakes have the most dramatic decrease in streamflow, particularly the Río Espiritu Santo watershed, where 82 percent of median flow is diverted.

Linking habitat stability to floods and droughts: effects on shrimp in montane streams, Puerto Rico

Covich A.P., Crowl T.A. & Scatena F.N. (2000) Linking
habitat stability to floods and droughts: effects on
shrimp in montane streams, Puerto Rico. Verhandlungen
der Internationalen Vereinigung fu¨r Theoretische und
Angewandte Limnologie, 27, 2430–2434.

Abstract: 
Most previous studies on Caribbean flood and drought frequency have examined hydrological (e.g. MORRIS & VAZQUEZ 1990, GARCIA et al. 1996) rather than ecological effects (COVICH et al. 1998). We analyzed temporal and spatial distributions of rainfall, stream flow, and mean maximum pool depth over an 8-year period (1990–1997) to evaluate effects of variable flows. We examined the response of a biotic variable (the coefficient of variation in shrimp densities) to changes in water depth (coefficient of variation of maximum pool depth) along an elevational gradient.

FLASHINESS INDICES FOR URBAN AND RURAL STREAMS IN PUERTO RICO

Abstract: 
Urbanization and increases in impervious area are known to increase stream runoff and flashiness and several indices have been developed to quantify flashiness in temperate streams. The effectiveness of these indices in the humid tropics and how urbanization influences the flashiness of tropical streams that are known for their inherent flashiness is poorly understood and documented. This study compares two existing flashiness indices and a new approach that quantifies flashiness by the average time between large events on 13 urban to forested streams in Northeastern Puerto Rico. The average time between events of specific magnitudes, the Richards-Baker Flashiness index, and a Frequency of Stage Change approach were calculated and compared using average daily, hourly, and 15 minute discharge data. All analysis was based on USGS discharge records for the same 10 year period, 2000 through 2009. The results indicate that when flashiness is based on average daily stream flow, there was little to no discernible difference in the flashiness of the urban and forested streams. This results because average daily discharge records miss or underestimates the magnitude, duration, and the frequency of most events. When comparing the time between events of a given magnitude using hourly or 15 minute discharge series, the urban drainages have a shorter time period between peaks of a given magnitude than rural drainages. The Frequency of Stage Change approach also indicates that high density urban drainages are flashier than drainages with forested or mixed land use. For the average days and the stage frequency change method, flashiness indices based on hourly time series are similar to those based on the 15 minute series. The analysis indicates that tropical urban streams are flashier than their rural counterparts; however the difference is less than has been reported in temperate studies and is only statistically apparent when using high resolution discharge records.
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