Statistical Methods for Assessing Climatic and Anthropogenic Impacts on Streamflow, Storage Reservoir Yield, and Effectiveness of Water Conservation Programs.
Statistical methods are applied for evaluating the impacts of climatic and anthropogenic
influences on streamflow, for determining the ability of storage reservoirs for managing
hydrologic variability and for assessing the effectiveness of water conservation
programs. The impacts of changes in climate, land use and water use on both mean flows
and droughts across the Eastern U.S. ar... read moree estimated in terms of dimensionless elasticity
using three multivariate regression approaches. These three influences have never been
considered simultaneously in any previous research particularly with reference to floods
and droughts, and yet we find that such impact assessments for which only one influence
is considered are most likely to give biased estimates. Across the eastern U.S. both
mean and drought flows are found to be quite sensitive to changes in climate and land
use, with both mean and drought flows being most sensitive to precipitation except for
the New England Watershed (region 1), where the drought flows are most sensitive to
temperature. Across the eastern U.S., impacts of land use changes on both annual mean
and drought flows are quite significant. Particularly for region 1, where urbanization
is intense, the overall land use changes have greater impact than climate
(precipitation) on annual mean flow. The impact of water use on annual mean flow in
region 1 is found significant while for other regions impact of water use on both mean
and drought flows are insignificant. The impacts of precipitation (P) and potential
evapotranspiration (PET) on floods, droughts and mean flows across the continental U.S.
are evaluated simultaneously using two multivariate regression approaches. Remarkably no
previous research has evaluated climate impacts on mean, flood and drought flows
systematically across a national scale study area. Stochastic based regression
approaches are found to provide better fits than their deterministic counterparts. Flood
flows are found to be more sensitive (1) to both P and PET for basins with a drier
climate, (2) to P for basins with less snow, smaller drainage areas, smaller
lakes/wetlands area, smaller soil permeability and steeper terrains, and (3) to PET for
basins with more snow and flatter terrains. Drought flows are found to be more sensitive
(1) to P for basins with a wetter climate, larger lakes/wetlands areas for attenuating
runoffs and lower baseflow, and (2) to PET for basins with a drier climate and smaller
soil permeability. This study further documents the importance of spatial and temporal
scales on estimation of the climate elasticity of streamflow. An optimization model is
combined with generalized storage-reliability-yield relationships to determine the
optimal capacities and locations of additional storage reservoirs needed for the Zambezi
River Basin. Since economic growth within the Zambezi River Basin thrives on provision
of high reservoir yield reliability which also results in a reduction of hydrologic
variability downstream to a reservoir, we advocate use of yield reliability for
quantifying the hydrologic variability associated with reservoir planning and
operations. In addition, the results of the optimization analysis suggest the locations
within the region where additional storage capacities are needed. Finally, the
effectiveness of four water conservation programs is evaluated using controlled
experiments in four towns within the Ipswich River Watershed in Massachusetts. This
study introduces nonparametric statistical methods, which have seldom been applied in
similar previous research, for evaluating the effectiveness of these conservation
programs in reducing water use. Installation of weather-sensitive irrigation controller
switches (WSICS) in municipal ball fields, free residential water use audits with water
fixture retrofit kits, rebates for low-water-demand toilets and washing machines, and
soil amendments in ball fields are found to reduce water use significantly. Installation
of WSICS in residences is found to be more effective in reducing water use of high water
users. Rainwater harvesting is found to provide substantial rainwater use, but these
volumes are small relative to total domestic water use and relative to the natural
fluctuations in domestic water use.
Thesis (Ph.D.)--Tufts University, 2012.
Submitted to the Dept. of Civil Engineering.
Advisor: Richard Vogel.
Committee: Sara Cohen, Stephen Levine, and Jeffrey Zabel.
Keywords: Hydrologic sciences, and Water resources management.read less