In city pollution monitoring, sensor nodes attached to buses collaborating with a sensor network distributed across the city would be an efficient tool to monitor pollution and presence of contaminants, both during normal city life and in case of emergency (e.g., for the detection of nuclear, chemical threats). In these large scale applications, deployment of multiple sinks is required for efficient data gathering from WSNs. A typical way of extracting information from a sensor network is to disseminate special messages, namely _queries_, from sink nodes to sensor nodes, asking them to send data which have the properties specified in the queries. The main consideration in designing query dissemination algorithms is to efficiently forward queries from sink nodes to sensor nodes. Especially, in a multi-sink sensor network if a query is only valid in particular regions of the deployment, it is important to determine which sinks need to inject the query to reach all sensor nodes in the area of interest. The simplest approach to deliver a message to all nodes within a geographical region (_i.e._, geocasting) is _simple flooding_ of the message from all sinks in the whole network irrespective of the destination region and coverage areas of the sinks. Since simple flooding is not an efficient approach in terms of communication overhead, another class of geocasting approaches, called _directed flooding_, has been proposed [3] to limit message overhead and network congestion by defining forwarding zone, which comprises a subset of all nodes in the network. To employ directed flooding in a multi-sink sensor network, the network should inform sinks what geographical area is covered by which sink. This requires partitioning (clustering) of the network between different sinks, which is generally performed using energy-aware or any other metric-based route selection schemes. Data collection/extraction in WSNs is often performed by using one of the fundamental approaches, tree-based routing that forms a spanning tree rooted at the sink [4]. In a multi-sink WSN, the tree-based routing combined with multi-sink partitioning forms multiple routing trees rooted at different sinks, where each sensor node in the network is connected to only one sink (e.g., the closest sink). In our previous work [5, 6], we design and evaluate a geocasting protocol for query dissemination called GeoCHT, which uses forwarding zones defined by local coverage areas of sensors and sinks in a tree-based network. The local coverage area of a sensor node in a tree-based routing is made of all descendant nodes of this sensor node. Figure 1 illustrates local coverage areas of a sink and sensor nodes. In the figure, the local coverage area of a node, for instance, node x, covers all its descendants. The local coverage area of the sink covers all the nodes in the tree. The local coverage areas are used for efficient geocasting of queries from the sinks towards an area of interest. Coverage area based geocasting restricts the area in which the queries are forwarded, thus achieves energy saving in a WSN. It also directs the queries towards the region of interest, as a results decreases the query delivery delay. In our previous work, the maintenance (due to topology changes such as node failures or mobility) of the routing structure (_i.e._, trees and coverage areas) is done by global reconstruction of the whole structure periodically. In global updating, sinks trigger the updating process by flooding special messages (called _hello_ packets) over the network. Global updating forms a reliable routing structure for query dissemination. However, it may result in high energy consumption since it also updates the parts of the structure that are not affected by topology changes. In this paper, we address the limitations and drawbacks of our previous updating approach and focus on handling topology changes due to sensor mobility. The final goal is achieving reliable geocasting of queries in multi-sink WSNs in an energy efficient way.