The establishment of Water Management Boards (WMBs) in India often becomes a contentious issue due to the complex interplay of constitutional provisions, inter-state relations, socio-economic factors, and political dynamics. Here are the primary reasons for the controversy:

1. Constitutional Provisions and State Subject: Water is primarily a 'State Subject' under Entry 17 of List II (State List) of the Seventh Schedule of the Indian Constitution. This means states have legislative and executive powers over water resources. Any move to establish central or inter-state WMBs is often perceived by states as an encroachment on their constitutional autonomy and a dilution of their control over a vital resource.

2. Inter-State Water Disputes: India has a long history of inter-state river water disputes (e.g., Cauvery, Krishna, Mahanadi). States are highly protective of their share of water. WMBs, especially those with a mandate to manage inter-state rivers, are viewed with suspicion by riparian states, fearing that their interests might be compromised or that the board might favor one state over another.

3. Centralization of Power: Proposals for WMBs, particularly those with significant central government involvement or broad powers, are often seen as an attempt to centralize water governance. States argue that local conditions, needs, and priorities are best understood and managed at the state or local level, and a centralized body might not be responsive to these nuances.

4. Loss of Local Control and Representation: Local communities, farmers, and district administrations often fear that WMBs might bypass existing local governance structures (like Panchayati Raj Institutions) and reduce their say in water resource management. Concerns about adequate representation of all stakeholders, including marginalized communities, are also frequently raised.

5. Funding and Resource Allocation: The financial implications of WMBs, including their funding mechanisms and how they allocate resources (both water and financial), can be a major point of contention. States may be reluctant to cede control over revenue generation or expenditure related to water projects to an external board.

6. Operational Autonomy vs. Accountability: While WMBs are often proposed for their technical expertise and ability to make impartial decisions, questions arise about their operational autonomy from political interference and their accountability to the public and elected bodies. Without clear frameworks, they can become bureaucratic and ineffective.

7. Impact on Existing Institutions: India already has various water-related institutions at central, state, and local levels. The creation of new WMBs can lead to jurisdictional overlaps, conflicts, and a lack of clarity regarding roles and responsibilities, potentially undermining existing efforts.

In essence, the controversy stems from a fundamental tension between the need for integrated, basin-level water management (often requiring a supra-state body) and the constitutional framework that vests primary control over water with individual states, coupled with deep-seated inter-state rivalries and local concerns.