The high scientific standards maintained by Hydrology Research in its papers owe much to the continuing dedication of the journal's reviewers, who give freely of their time and expertise. IWA Publishing is pleased to pay tribute to this contribution by recognizing those who have participated in the review process. Thus, the Editors of Hydrology Research acknowledge with particular gratitude the following reviewers who have reviewed papers during the period January 2020–December 2020.
| Ali A. Assani | Ahmed El-Shafie | Amin Kiaghadi | Vincent Odongo | Yanguo Teng |
| Ismail Abustan | Ahmed Elshall | Hung Soo Kim | Jarkko Okkonen | Pei Tian |
| Bachir Achour | Kolbjørn Engeland | Kue Bum Kim | Charles Onyutha | Tibebe Tigabu |
| Arash Adib | Haiyan Fang | Sunmin Kim | Yun Pan | Dimitris Tigkas |
| farshad Ahmadi | Omid Fathizadeh | Ozgur Kisi | Bo Pang | Ali Torabi Haghighi |
| Kamal Ahmed | Svenja Fischer | Nils-Otto Kitterød | Daniele Pedretti | Martyn Tranter |
| Pertti Ala-aho | Carina Furusho | Michael Kizza | Tao Peng | Hristos Tyralis |
| Gholamreza Andalib | Tamer Gado | Thomas Kjeldsen | Marco Perez Hernandez | Mehdi Vafakhah |
| María Guadalupe Ares | Michał Gałkowski | Bjørn Kløve | Simone Persiano | Emmanouil Varouchakis |
| Hazi Azamathulla | Sigurdur Gardarsson | Krzysztof Kochanek | Fotios-Konstantinos Pliakas | Sundar Venkat |
| Hamidreza Babaali | Chandra Prasad Ghimire | Harri Koivusalo | Thomas Poméon | Anthi Eirini Vozinaki |
| Mehdi Bahrami | Mohammad Ali Ghorbani | Sjur Kolberg | Mohsen Pourreza-Bilondi | Alexandre Wadoux |
| Liping Bai | Yicheng Gong | Nektarios Kourgialas | Arvydas Povilaitis | Dagang Wang |
| Ryan Bailey | Salvatore Grimaldi | Jurate Kriauciuniene | Satya Prakash | Dong Wang |
| Hannah Bailey | Jannis Groh | Marie Larocque | Ilaria Prosdocimi | Lei Wang |
| James Ball | Carolina Guardiola Albert | Henning Lebrenz | Jaan Pu | Tiejun Wang |
| Nicole Balliston | Ayse Yeter Günal | Hong Li | Nevil Quinn | Weiguang Wang |
| Reza Barati | Qingchun Guo | Jianzhu Li | Omid Rahmati | Xiaocui Wang |
| Andras Bardossy | Shenglian Guo | Lu Li | Seshadri Rajagopal | Zhanli Wang |
| Michel Bechtold | Wenzhao Guo | Weiyue Li | Yousef Ramezani | Howard Wheater |
| Maria Bermudez | Bangshuai Han | Xiangzhong Li | Kabir Rasouli | Ming-ko Woo |
| Miriam Bertola | Songjun Han | Xianghu Li | Arun Ravindranath | Gao-Lin Wu |
| Enoch Bessah | Cameron Harrington | Yunliang Li | Fozia Rehman | Jinkui Wu |
| Daniela Biondi | Kay Helfricht | Zhanling Li | Emma Robinson | Songbai Wu |
| Andrew Black | Hans Jørgen Henriksen | Wei Liang | Prabin Rokaya | Hongxia Xu |
| Morten Borup | Reinhard Hinkelmann | Haiqing Liao | Emanuele Romano | Yueping Xu |
| Michael Bruen | Glenn Hodgkins | Kairong Lin | Renata Romanowicz | Lei Yan |
| J Peter Burgess | Amanda Holder | Ian Littlewood | Noori Roohollah | Chuanguo Yang |
| Tommaso Caloiero | Mojtaba Hosseini | Bingjun Liu | Dan Rosbjerg | Pingheng Yang |
| Enrica Caporali | Aida Hosseini Baghanam | Liu Liu | Joaquín Sánchez | Ting Yang |
| Markus Casper | Baodeng Hou | Xiaomang Liu | Reshmi Sarkar | Zhibing Yang |
| Artemi Cerdà | Bin Hu | Dalila Loudyi | Alfonso Senatore | Cheng Yao |
| Venu Chandra | Caihong Hu | Athanasios Loukas | Junejo Shafique | Lili Yao |
| Liang-Cheng Chang | Litang Hu | Lifeng Luo | Wei Shangguan | Zaher Yaseen |
| K.W. Chau | Guoru Huang | Pingping Luo | Songdong Shao | Zaher Mundher Yaseen |
| KwoK Wing Chau | Shengzhi Huang | Wei Luo | Sangam Shrestha | Xuwang Yin |
| Chao Chen | Wen-Cheng Huang | Jason Lynch | Dharmaveer Singh | David J. Yu |
| Hua Chen | Catherine Hughes | Neil MacDonald | Shallesh Kumar Singh | Guoan Yu |
| Xi Chen | Shouliang Huo | Rodrigo Manzione | Thomas Skaugen | Songyan Yu |
| Alexander Cobb | Marijke Huysmans | Miguel Angel Marazuela | Jon Skoien | Xing Yuan |
| Maggie Creed | Eun Soon Im | Pau Martí | Leszek Sobkowiak | Weifeng Yue |
| Barry Croke | Cong Jiang | Rangaswamy Mohanraj | Xiaomeng Song | Ismail Yusoff |
| Christophe Cudennec | Dejuan Jiang | Eugenio Molina Navarro | Asgeir Sortberg | Antonio Zarlenga |
| Junfeng Dai | Jiping Jiang | Ameer Muhammad | Konstantinos Soulis | Yuanzheng Zhai |
| Ali Danandeh Mehr | Juying Jiao | Tone Muthanna | Virginia Stovin | Hongbo Zhang |
| Giuseppe Del Giudice | Emmanuel Jjunju | Sujay Naganna | Xiaosi Su | Qi Zhang |
| Vitali Diaz Mercado | Seifeddine Jomaa | Mohammad Najafzadeh | Yanjun Su | Wenxia Zhang |
| Andre Diniz | Collin G. Joseph | Zoran Nakic | G Sun | Yu Zhang |
| Qianjin Dong | Mark Jury | Aikaterini Nanou-Giannarou | Wenchao Sun | Boyuan Zhu |
| Weili Duan | Sepideh Karimi | Mohammad Nazeri Tahroudi | Xun Sun | Li Zongxing |
| Noam Dvory | Giri Kattel | Cosmo Ngongondo | Adam Szymkiewicz | Rui Zuo |
| Uwe Ehret | Richard Keim | Like Ning | Amin Talei | |
| Gozen Elkiran | Mohsen Khatibinia | Enda O'Connell | Mouleong Tan |
