The better water supply system in the United States is the combination of surface water and groundwater systems. This dual-source approach provides a more reliable and resilient water supply compared to relying solely on one source. According to the U.S. Environmental Protection Agency (EPA), surface water systems provide approximately 85% of the nation's drinking water, while groundwater systems supply about 15%. This diversity in sources ensures a more consistent water supply, as surface water can be supplemented by groundwater during periods of drought or high demand.

The resilience of a dual-source water supply system is evident in the data. For instance, during the severe drought in California from 2011 to 2017, the state's groundwater reserves played a crucial role in maintaining water supply stability. The California Department of Water Resources reported that groundwater pumping increased significantly during the drought, accounting for about 60% of the state's water supply. This reliance on groundwater helped mitigate the impact of the drought on water availability.

Moreover, dual-source systems offer a more sustainable approach to water management. Groundwater can act as a buffer against the variability of surface water supplies, reducing the risk of water shortages. The EPA's 2016 report on water infrastructure indicates that integrated water resource management, which includes both surface water and groundwater, can lead to more efficient use of water resources and reduced environmental impacts.

In addition, dual-source systems often benefit from better water quality. Groundwater typically undergoes natural filtration through soil and rock, which can improve its quality compared to surface water. The American Water Works Association (AWWA) notes that groundwater is often free from many of the contaminants found in surface water, making it a safer option for drinking water.

In conclusion, the combination of surface water and groundwater systems is the better water supply system in the United States. This dual-source approach provides resilience, sustainability, and improved water quality, as evidenced by data from the EPA and the California Department of Water Resources.