Houthi group continues to obstruct peace efforts and push towards an unprecedented exacerbation of the humanitarian situation, despite warnings of the international relief organizations, which confirmed that three-quarters of the population would have no access to water and sanitation services over the next year. A joint methodological note on the conditions of water and sanitation services explained how the number of People in Need (PIN) of Water, Sanitation, and Hygiene (WASH) assistance and the WASH Severity Scores for each district in Yemen would be calculated for the 2023 Yemen Humanitarian Needs Overview (HNO). The organizations pointed out that Yemen has been the world's worst humanitarian crisis during the past five years, and the humanitarian situation remains critical as the country enters its eighth year of the war. The humanitarian situation in Yemen remains critical, with economic decline and protracted armed conflict causing many Yemenis to need assistance. The conflict has further aggravated the country's underlying food insecurity while compromising essential services and infrastructure, including health and education, and significantly damaging the economy and the social fabric. The joint note stated that Yemen remained the sixth largest internal displacement crisis globally, with an IDP population of over 4.3 million. In the 2022 HNO, the Yemen WASH Cluster (YWC) reported an increase from 2021 in the number of people in need of support to meet their WASH needs by 16 percent (17.8 million people in need), while the number of people in acute needs increased by 28.7 percent (11.2 million people in acute need). According to these numbers, less than a quarter of the population has access to safe WASH services. The note warned that despite these pressing needs, global funding has fallen short of meeting all required budget for WASH by $2.7 billion, stressing the need to identify and prioritize the communities most in need and determining their vulnerabilities and risks. To understand the WASH needs, risks, and vulnerabilities of the population in Yemen, the 2023 HNO assesses WASH-related indicators across all districts in Yemen. The YWC has partnered with REACH to produce an analysis of these indicators to determine the number of populations in need, and the severity of needs, by demographic group and geographic location. The document outlines using indicators and resources for informing the HNO, building these indicators, scaling the severity of needs, and calculating the number of populations in need.