In 1981, the government established the National Urban Water Authority (NUWA) and charged it with the responsibility to develop and manage urban water supply on Tanzania Mainland. NUWA, which became operational in 1984, set a target to take over and reform water supply services in all urban areas in Dar es Salaam. The government re-organized NUWA in 1997 to form the Dar es Salaam Water and Sewerage Authority by merging the functions of NUWA and the sewerage functions of the Sewerage and Sanitation Department of the City Commission. Under the DAWASA Act, DAWASA was made responsible for operating and maintaining all water supply and sewerage services in Dar es Salaam and its satellite towns of Bagamoyo and Kibaha.

The DAWASA area of operations incorporates the City of Dar es Salaam and the towns of Kibaha, Bagamoyo and the corridors of its two transmission lines. DAWASA is responsible for providing water supply services to its customers (about 419,265) in its area of operations. DAWASA also provides sewerage services to a small number of customers (around 4,691) in the city of Dar es Salaam. By the late 1990s, it was evident that DAWASA was unable to respond quickly enough to meet customer demands for improved levels of service and improved finances to adequately maintain and replace its aging assets.

In August 1997 the African Development Bank (AfDB) identified a Dar es Salaam Water Supply and Sanitation Project that would focus on rehabilitating and improving operations and facilities with DAWASA as the service provider and operator. AfDB put project processing on hold pending the outcome of consultations in 1997/98 between operators and the Government of Tanzania for a long term “Concession”. Under the proposed arrangements the concessionaire was to be responsible for financing the investment programme estimated to cost about US 24,250 million as well as operation and maintenance activities. In November 1998 it became clear that this approach was not going to succeed. Private investors were unwilling to finance such a venture in Dar es Salaam given the state of the Water Supply and Sanitation (WSS) operations and infrastructure. Consequently, the government requested World Bank assistance to design an option that would combine private operation and public financing. In March 2003 DAWASA completed the preparation of the Dar es Salaam Water Supply & Sanitation Project (DWSSP) in keeping with the suggested scope defined by the World Bank. The World Bank, African Development Bank and the European Investment Bank appraised the project and commenced negotiations for financing.

DAWASA and City Water Services (CWS) met all conditions precedent for external financing and the project and lease contracts became effective 1 August 2003. The Lease Contract with City Water Services was terminated on 31st May 2005 after attempts to renegotiate the contract failed.
Main reasons for termination was breach of the lease the lease contract which included:-

Non payment of the rental fees,

Non remittance of the lessor tariff,

Non deposit into the First Time New Domestic Water Supply Connection Fund (FTNDWSCF),

CWS could not inject funds in the rehabilitation project and

Failure to attain performance targets.

Upon termination of the CWS Lease Contract DAWASA appointed the Dar es Salaam Water and Sewerage Corporation (DAWASCO) as the new operator for the DAWASA Service Area. DAWASCO was established in May 2005 under the Public Corporations Act 1992. Following negotiations DAWASA and DAWASCO signed a new ten-year Lease Contract effective 1 July 2005 the contract was extended to 2018 to allow the government to merge the two utilities.
On September 2018, DAWASA and DAWASCO merged and continued to perform functions and duties as specified in the DAWASA Act number 20 of 2001.
The water supply and Sanitation Act no 5 of 2009 came in to operation on July 1^st 2019 through Government Notice No. 460 of 2019 published on June 14^th 2019. With the new Act in place, DAWASA changed its name to Dar es salaam water supply and Sanitation Authority. Also the Act no 05/2019 established the rural water supply and sanitation agency RUWASA which is responsible for implementing and overseeing water supply and sanitation projects in rural areas, thus water supply Departments in Dar es salaam were abolished and activities implemented therein were transferred to DAWASA.

On September 6^th 2019 the Government rough GN No. 660/2019 established the Dar es salaam Water Supply and Sanitation Authority and dis established Kisarawe and Mkuranga water Supply and Sanitation authorities by extending its operations to DAWASA.

On 31^st January 2020 the Government through a government notice No. 71 of 2020 dis-established CHALIWASA and extended the DAWASA service area to include Chalinze town and part of or villages in Bagamoyo District Council, Kibaha District Council and Morogoro Rural District Council.