Revenues

Most of Registrant's revenues are derived from contracts with customers, including tariff-based revenues from its regulated utilities. ASUS's 50-year firm fixed-price contracts with the U.S. government are considered service concession arrangements under ASC 853 Service Concession Arrangements. Accordingly, the services under these contracts are accounted for under Topic 606 Revenue from Contracts with Customers and the water and/or wastewater systems are not recorded as Property, Plant and Equipment on Registrant’s balance sheet.

Although GSWC has a diversified base of residential, commercial, industrial and other customers, revenues derived from residential and commercial customers accounted for approximately 90% and 85% of total water and electric revenues, respectively, during each of the three months ended March 31, 2019 and 2018. The vast majority of ASUS's revenues are with the U.S. government. For the three months ended March 31, 2019 and 2018, disaggregated revenues from contracts with customers by segment were as follows:



	Three Months Ended March 31,
(dollar in thousands)	2019			2018
Water:
Tariff-based revenues	$	59,575		$	65,775
Surcharges (cost-recovery activities)	291			793
Other	459			442
Water revenues from contracts with customers	60,325			67,010
WRAM under (over)-collection (alternative revenue program)	4,398			(2,598		)
Total water revenues	64,723			64,412

Electric:
Tariff-based revenues	11,266			10,019
Surcharges (cost-recovery activities)	54			47
Electric revenues from contracts with customers	11,320			10,066
BRRAM over-collection (alternative revenue program)	(691		)	(234		)
Total electric revenues	10,629			9,832

Contracted services:
Water	13,355			13,000
Wastewater	13,026			7,484
Contracted services revenues from contracts with customers	26,381			20,484

Total revenues	$	101,733		$	94,728

The opening and closing balances of the receivable from the U.S. government, contract assets and contract liabilities from contracts with customers, which related entirely to ASUS, were as follows:



(dollar in thousands)	March 31, 2019		January 1, 2019

Receivable from the U.S. government	$	60,011	$	61,126
Contract assets	$	29,460	$	24,447
Contract liabilities	$	10,426	$	7,530

Contract Assets - Contract assets are those of ASUS and consist of unbilled revenues recognized from work-in-progress construction projects, where the right to payment is conditional on something other than the passage of time. The classification of this asset as current or noncurrent is based on the timing of when ASUS expects to bill these amounts.

Contract Liabilities - Contract liabilities are those of ASUS and consist of billings in excess of revenue recognized. The classification of this liability as current or noncurrent is based on the timing of when ASUS expects to recognize revenue.

Revenue for the three months ended March 31, 2019, which was included in contract liabilities at the beginning of the period was not material. Contracted services revenues recognized during the three months ended March 31, 2019 from performance obligations satisfied in previous periods were not material.

As of March 31, 2019, Registrant's aggregate remaining performance obligations, which are entirely for the contracted services segment, were $3.2 billion. Registrant expects to recognize revenue on these remaining performance obligations over the remaining term of each of the 50-year contracts, which range from 36 to 49 years. Each of the contracts with the U.S. government is subject to termination, in whole or in part, prior to the end of its 50-year term for convenience of the U.S. government.