Siyu LiFollow

Date of Award

Fall 2024

Language

English

Embargo Period

11-23-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Environmental and Sustainable Engineering

Program

Environmental and Sustainable Engineering

First Advisor

Yaoze Liu

Committee Members

Yaoze Liu, Rixiang Huang, Kyoung-Yeol Kim, Xiaobo X Romeiko

Keywords

Green infrastructure (GI), efficiency, urban hydrology, stormwater management, Soil and Water Assessment Tool (SWAT), future climate

Subject Categories

Climate | Hydrology | Sustainability | Water Resource Management

Abstract

Urbanization and climate change have detrimental impacts on water quantity and quality. Rainwater harvesting/reuse for landscape irrigation with rain barrels/cisterns, which can assist urban hydrological/water quality restoration and provide a beneficial resource for irrigating landscape, holds significant potentials in urban areas under current and future climates. However, the impacts of rainwater harvesting/reuse strategies for landscape irrigation under a changing climate need to be comprehensively evaluated to assist decision-making. In addition, a comprehensive tool is needed to help stakeholders develop efficient strategies to harvest rainwater for landscape irrigation with rain barrels/cisterns.

To address the needs, the simulation of the sub-daily hydrological impacts of rainwater harvesting for landscape irrigation with rain barrels/cisterns in the Soil and Water Assessment Tool (SWAT) was improved, including the simulation of rainwater harvesting with rain barrels/cisterns, rainwater reuse for auto landscape irrigation, evapotranspiration, initial abstraction, impervious area, soil profile, and lawn management operation. The improved SWAT was applied in the urbanized Brentwood watershed (Austin, TX) to evaluate its applicability and investigate the impacts of rainwater harvesting and reuse strategies on the reductions and reduction efficiencies (reductions per volume of rain barrels/cisterns implemented) of field scale runoff (peak and depth) and watershed scale streamflow (peak and volume) for two storm events. Scenarios explored included different sizes of rain barrels/cisterns, percentages of rooftop areas with rain barrels/cisterns implemented, auto landscape irrigation rates, and landscape irrigation starting times. The performance of rainwater harvesting and reuse strategies, which is determined by features of fields, watersheds, and storm events, varied for different reduction goals (streamflow or runoff, and peak or depth/volume). To achieve sustainable urban stormwater management, the improved SWAT model has enhanced capability to help stakeholders create efficient rainwater harvesting and reuse strategies to reduce field scale runoff and watershed scale streamflow.

Then, the simulation of urban drainage networks in the SWAT was further improved by coupling the Storm Water Management Model (SWMM)’s closed pipe drainage network (CPDN) simulation methods with the SWAT model that was previously improved for simulating the impacts of rainwater harvesting for landscape irrigation with rain barrels/cisterns. The newly improved SWAT or SWAT-CPDN was applied to simulate the urban hydrology of the Brentwood watershed (Austin, TX) and evaluate the long-term effects of rainwater harvesting for landscape irrigation with rain barrels/cisterns at the field and watershed scales. The results indicated that the SWAT-CPDN could improve the prediction accuracy of urban hydrology with good performance in simulating discharges (15 min, daily, and monthly), evapotranspiration (monthly), and leaf area index (monthly). The impacts of different scenarios of rainwater harvesting and reuse strategies (rain barrel/cistern sizes, percentages of suitable areas with rain barrels/cisterns implemented, auto landscape irrigation rates, and landscape irrigation starting times) on each indicator (runoff depth, discharge volume, peak runoff, peak discharge, combined sewer overflow—CSO, freshwater demand, and plant growth) at the field or watershed scale varied, providing insights for the long-term multi-functional impacts (stormwater management and rainwater harvesting/reuse) of rainwater harvesting for landscape irrigation with rain barrels/cisterns. The varied rankings of scenarios found for achieving each goal at the field or watershed scale indicated that tradeoffs in rainwater harvesting and reuse strategies exist for various goals, and the strategies should be evaluated individually for different goals to optimize the strategies. Efficient rainwater harvesting and reuse strategies at the field or watershed scale can be created by stakeholders with the assist of the SWAT-CPDN to reduce runoff depth, discharge volume, peak runoff, peak discharge, CSO, and freshwater demand, as well as improve plant growth.

Finally, this study assessed the changes in climate parameters (precipitation, temperature, solar radiation, relative humidity, and wind speed) considering four Shared Socioeconomic Pathways [SSPs] (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) over historical period (2000-2014) and future modeling periods (MP1: 2040-2059, MP2: 2060-2079, and MP3: 2080-2099) in the Brentwood watershed (Austin, Texas); and evaluated the impacts of rainwater harvesting/reuse strategies for landscape irrigation on discharge volume, peak discharge, CSO, freshwater demand, and plant growth under historical and future climates (SSPs and periods) using the SWAT-CPDN. Compared to the ensemble mean of climate parameters for historical climate, under future climates, precipitation (-5.57% to 0.01% changes), maximum temperature (6.99% to 18.65% changes), minimum temperature (17.55% to 35.13% changes), wind speed (-0.20% to 19.02% changes), and relative humidity (-8.35% to -0.07% changes) varied greatly; however, solar radiation (-0.01% to -0.02% changes) only varied slightly. Compared to the baselines (without rain barrels/cisterns), rainwater harvesting/reuse strategies with the most benefits under historical and future climates could reduce 8.43% to 8.89% of discharge volume, 4.74% to 5.76% of peak discharge, 5.00% to 6.20% of CSO, and 22.91% to 24.97% of freshwater demand; and retain plant biomass. No single rainwater harvesting/reuse strategy can maximize benefits across all indicators under varying climate conditions. The most beneficial rainwater harvesting/reuse strategies need to be obtained by evaluating their impacts on individual goals under each climate condition.

License

This work is licensed under the University at Albany Standard Author Agreement.

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