UVM Theses and Dissertations
Format:
Print
Author:
Stryker, Jody
Title:
Dept./Program:
Civil and Environmental Engineering
Year:
2012
Degree:
MS
Abstract:
This study uses a coupled hydrology-entomology model to investigate the role of land use change on the hydrological processes that impact malaria vector mosquito abundance in a water-limited, highland region of Ethiopia, Land use change affects the volume of water from overland flow that reaches small-scale topographic depressions, which constitute the primary breeding habitat of malaria transmitting Anopheles gambiae mosquitoes. We use a physically-based, distributed hydrology model to isolate specific hydrological mechanisms by which vegetation impacts pool formation and persistence, including partitioning of rainfall into infiltration and runoff, surface resistance to overland flow, and uptake by plant roots. An agent-based entomology model evaluates the non-linear response of mosquito populations to changes in habitat availability as a result of simulated variability in runoff volumes. This coupled hydrology-entomology model was applied to portions of a village in Waktola, Ethiopia, and reproduced observed interannual variability in mosquito abundance between the 2009 and 2010 wet seasons.
Several scenarios of various land cover were then evaluated using the calibrated and field-validated model. Model results show significant variation in pool persistence, pool depth, and surface area, and a corresponding effect on mosquito abundance, in response to changes in land use types. .) Increasing land use for locally-favored crops such as peppers by 25% produced a corresponding 28% increase in mosquito abundance compared to the 2010 baseline. It was also shown that responses in pool persistence and depth are largely sensitive to spatial proximity of vegetation changes to breeding habitat locations. Changing the vegetation classification of 10% of total land in the model domain from maize to pasture, where land altered was located directly surrounding pool locations, resulted in 44.3% higher mosquito abundance than the 2010 baseline.
The model showed sensitivity primarily to surface roughness but also to root zone uptake. This study indicates that land cover type, as well as spatial relations to breeding habitats, plays an important role in determining the formation and persistence of successful breeding habitats in water-limited environments, and thereby has an impact on mosquito abundance and malaria transmission. This study suggests that a more detailed representation of the role of vegetation in soil moisture variability and runoff generation would improve both regional malaria risk models and models that focus on smaller scale hydrological processes. This modeling approach can be applied to assess relative risk of malaria transmission as it is affected by expected and observed changes in land use and climate.
Several scenarios of various land cover were then evaluated using the calibrated and field-validated model. Model results show significant variation in pool persistence, pool depth, and surface area, and a corresponding effect on mosquito abundance, in response to changes in land use types. .) Increasing land use for locally-favored crops such as peppers by 25% produced a corresponding 28% increase in mosquito abundance compared to the 2010 baseline. It was also shown that responses in pool persistence and depth are largely sensitive to spatial proximity of vegetation changes to breeding habitat locations. Changing the vegetation classification of 10% of total land in the model domain from maize to pasture, where land altered was located directly surrounding pool locations, resulted in 44.3% higher mosquito abundance than the 2010 baseline.
The model showed sensitivity primarily to surface roughness but also to root zone uptake. This study indicates that land cover type, as well as spatial relations to breeding habitats, plays an important role in determining the formation and persistence of successful breeding habitats in water-limited environments, and thereby has an impact on mosquito abundance and malaria transmission. This study suggests that a more detailed representation of the role of vegetation in soil moisture variability and runoff generation would improve both regional malaria risk models and models that focus on smaller scale hydrological processes. This modeling approach can be applied to assess relative risk of malaria transmission as it is affected by expected and observed changes in land use and climate.