Abstract: SINCE THE FULL IMPLEMENTATION OF THE RIVER AND LAKE CHIEF SYSTEM, THE "RIVER (LAKE) CHIEF + PROCURATOR-GENERAL" COLLABORATIVE GOVERNANCE MODEL HAS EMERGED WIDELY ACROSS CHINA, REPRESENTING A SIGNIFICANT INSTITUTIONAL INNOVATION THAT OVERCOMES THE LIMITATIONS OF ADMINISTRATIVE LAW ENFORCEMENT IN AQUATIC ECOLOGICAL PROTECTION AND ADVANCES WATER GOVERNANCE UNDER THE RULE OF LAW. DRAWING ON THE FIVE ANNUAL VOLUMES OF A COMPILATION OF TYPICAL CASES IN THE COMPREHENSIVE IMPLEMENTATION OF THE RIVER AND LAKE CHIEF SYSTEM (2020–2024) COMPILED BY THE MINISTRY OF WATER RESOURCES AS THE CORE SOURCE MATERIAL, THIS STUDY SYSTEMATICALLY EXAMINES REPRESENTATIVE CASES, INCLUDING ZHANJIANG (GUANGDONG PROVINCE), THE ENTIRE HENAN PROVINCE, GUZHEN COUNTY (ANHUI PROVINCE), FENGXIAN DISTRICT (SHANGHAI), DAZU DISTRICT (CHONGQING), DONGYING CITY (SHANDONG PROVINCE), AND YANCHI COUNTY (NINGXIA). BASED ON THIS ANALYSIS, THE EXISTING PRACTICES ARE SYNTHESIZED INTO THREE INSTITUTIONAL MODELS. THE FIRST IS THE DUAL-TRACK COLLABORATIVE MODEL ("RIVER (LAKE) CHIEF + PROCURATOR-GENERAL"), WHICH EMPLOYS PUBLIC INTEREST LITIGATION AS ITS CORE INSTRUMENT, LEVERAGING THE PARALLEL OPERATION OF ADMINISTRATIVE ENFORCEMENT AND JUDICIAL SUPERVISION TO ACHIEVE LOW-COST, HIGH-DETERRENCE OUTCOMES. THE SECOND IS THE TRIPARTITE LINKAGE MODEL ("RIVER (LAKE) CHIEF + PROCURATOR-GENERAL + POLICE CHIEF"), WHICH ADDS CRIMINAL INVESTIGATION POWERS TO THE ADMINISTRATIVE AND PROSECUTORIAL FRAMEWORK, USING CRIMINAL DETERRENCE TO SEVER THE PROFIT CHAINS UNDERLYING "INTEREST-DRIVEN" VIOLATIONS. THE THIRD IS THE COMPREHENSIVE GOVERNANCE MODEL FEATURING "FOUR-CHIEF LINKAGE" (WATER RESOURCES ADMINISTRATION + PUBLIC SECURITY + PROCURATORATE + COURT), WHICH BUILDS A FULL-CHAIN CLOSED-LOOP SYSTEM INTEGRATING ADMINISTRATIVE ENFORCEMENT, PROSECUTORIAL SUPERVISION, CRIMINAL PROSECUTION, AND JUDICIAL ADJUDICATION THROUGH INSTITUTIONAL INTEGRATION. THESE THREE MODELS EXHIBIT SIGNIFICANT DIFFERENCES IN INSTITUTIONAL LOGIC, ACTIVATION THRESHOLDS, APPLICABLE SCENARIOS, AND DEGREES OF LEGAL FORMALIZATION. FROM THE LEGAL PERSPECTIVE OF SYNERGY BETWEEN PUBLIC INTEREST LITIGATION AND ADMINISTRATIVE ENFORCEMENT, THIS STUDY FURTHER EXAMINES THE INSTITUTIONAL FOUNDATIONS, OPERATIONAL MECHANISMS, AND BOUNDARY LIMITATIONS OF EACH MODEL, SYSTEMATICALLY SCRUTINIZING DEEP-SEATED RISKS SUCH AS ADMINISTRATIVE DEPENDENCY, CAMPAIGN-STYLE ENFORCEMENT, JURISDICTIONAL OVERREACH, AND REGIONAL DISPARITIES. FINALLY, THE PAPER PROPOSES CONCRETE PATHWAYS FOR TRANSITIONING THE "RIVER (LAKE) CHIEF + PROCURATOR-GENERAL" MECHANISM FROM LOCAL EXPERIMENTATION TO NATIONWIDE INSTITUTIONALIZATION, FROM NORMATIVE DOCUMENTS TO LEGAL AUTHORIZATION, AND FROM EPISODIC PRACTICES TO NORMALIZED PROTOCOLS, THEREBY PROVIDING THEORETICAL SUPPORT FOR DEEPENING THE RIVER AND LAKE CHIEF SYSTEM TOWARD "SUBSTANTIVE ACCOUNTABILITY AND EFFECTIVE FUNCTIONALITY" DURING THE 15TH FIVE-YEAR PLAN PERIOD (2026–2030).