Açude Lagoa do Arroz is a reservoir located in the municipality of Cajazeiras, in the alto sertão of Paraíba, near the border with Ceará. It sits in the valley of the riacho Cacaré, a tributary of the rio do Peixe, within the upper Piranhas river basin, approximately 420 km from João Pessoa and 360 km from Fortaleza. The reservoir was designed and built by the Departamento Nacional de Obras Contra as Secas (DNOCS), with construction running from 1983 to 1987.

The water body holds a storage capacity of approximately 80 million cubic meters and covers an inundated area of 1,228 hectares when full, making it a substantial body of open water in an otherwise arid landscape. The reservoir is capable of regulating a flow of 0.96 cubic meters per second. The surrounding terrain is characteristic of the northeastern Brazilian sertão — semi-arid, with caatinga vegetation and a landscape shaped by periodic drought.

Water levels can vary considerably depending on rainfall patterns, which are highly seasonal in this region. The sertão experiences a concentrated rainy season, and the reservoir's level is notably better following periods of precipitation. Paddlers should be aware that water levels may be significantly reduced during prolonged dry spells, which can affect the navigable area.

The shoreline is accessible by roads that run around the reservoir, and bank access is relatively straightforward. The community of Bom Jesus maintains a fishing colony on the margins of the reservoir, and artisanal fishing is an active and established use of the water. Tilápia and piau are the primary fish species present. The proximity to Cajazeiras — the main city of the region — means that hotels, restaurants, and commercial services are available nearby for those planning multi-day trips. The reservoir is also geographically close to Açude Engenheiro Ávidos and the Barragem de São Gonçalo, which could be incorporated into a broader exploration of the area's water bodies.