Current work intends to develop a management tool that will help better understand the impact of land use on forested watershed hydrology and water quality. Findings of this research program will be helpful for many national and state programs in Hawaii. The end users of the land-user management tools are state, local and federal agencies in addition to watershed managers. The main goal of this long-term research plan is to develop an integrated research approach at the forested watershed continuum by combining multi-scale field experiments with a strong numerical modeling to enhance our understanding of watershed hydrological processes, water yield and water quality as a result of variation of different controlling parameters, i.e., land use (reforestation/deforestation, invasive species, agricultural use, urbanization) extreme weather conditions (drought, flooding).

Contact
Dr. Ali Fares (afares@hawaii.edu)
Phone: 808-956-6361
Fax: 808-956-6539

FUNDING has been provided to CTAHR for this research from the USDA Cooperative State Research, Education, and Extension Service Project HAW00134-M.

OBJECTIVES

1) Evaluate the potential of different watershed scale models to be used under Hawaii conditions:
i) Because a variety of models show promise for achieving our intended objectives of watershed modeling, a literature review is necessary to help select the two best numerical model candidates that will be further tested;
ii) Examine applicability of governing equations, assumptions and required input parameters by each model;
iii) Modify and improve chosen models, if needed, to fit small watershed conditions.

2)Develop a set of management tools to enable researchers, watershed managers, regulator and different stake holders to predict different short- and long-term land management scenarios and impact of extreme weather conditions:
i)Assess the minimum data needed to use the model reasonably;
ii)Make and test projections about future development and its ecological implications, and compare stream health measures under different geographical patterns of development;
iii) link the land use change and hydrologic response model with scientifically derived projections of ecological conditions in the associated watersheds to assess how specific arrangements of development influence ecological conditions at a variety of geographic scales.

APPROACH

1) Model selection: There are different potential models to choose from that can be used to model the watershed hydrology. The following criteria will be used in selecting the appropriate model: a) Deterministic models where the input parameters are measurable and have physical meaning at the opposite of black box type models. b) Integrated model that simulates rainfall-runoff and surface subsurface processes. c) User friendly so it can be used by other interested people. 2) Model calibration: a) Compilation of existing input data required by the model and compilation of ancillary data and observational data for model calibration. b) Development of a model calibration strategy through implementation of existing software for general inversion and calibration of multi-parameter hydrological models. c) calibration of hydrological and water-quality model (sediment and nutrients). 3) Model validation: a) Use some of the data for validation of the selected model. b) Compare simulated and field data 2) Phase II Alternative watershed management scenarios Evaluating alternative management strategies through experiments and a limited amount of field measurements is not feasible, and a modeling study is often the only viable means of providing input to management decisions. Several potential scenarios will be simulated based on practical land use alternatives appropriate to the watershed. This will forecast future development patterns to different stakeholders. With this modeling exercise we will assess how various growth patterns are likely to influence different hydrological components of the watershed. Through collaboration with different stakeholders, i.e., local government policy-makers and scientists, we will evaluate the effectiveness of current land use policies and restoration programs in minimizing the negative consequences of some land use conversion in different watersheds.

Forested watershed management is complex and requires integration of different expertise in different areas. Little is known about the impact of change in land use, i.e, re-forestation/deforestation on watershed hydrology under Hawaii conditions. Current work intends to develop a management tool that will help better understand the impact of land use on forested watershed hydrology and water quality. During this year efforts in this project were concentrated on complementing those of a companion project: "Determining the impacts of water pumping and alien species invasion on stream flow for a sustainable water resource management in Makaha Valley, Hawaii." We conducted sub-watershed soil water content monitoring calibrations. An undergraduate student was trained as part of this project.

The out of this project will help in the process of determining a management tool for Hawaiian wateshed to predict the effect of different land uses. This tool will be a good teaching tool for different people, i.e., students.

PUBLICATIONS (not previously reported): 2005/10 TO 2006/09

Domingos Maria, A. Fares, A. Mair, and Hamdhani. Laboratory Calibration of Two Soil Water Content Measuring Capacitance Sensors in Two Tropical Soils. Proceedings of CTAHR 18th Annual Student Research Symposium. April 7-8 2006. Honolulu,