A distributed sensor network (DSN) consists of sensor nodes with limited energy source, sensor devices, short-range radio and on-board processing capability. Sensing capability of the attached sensing devices and their small size, make these sensor nodes highly suitable for environmental monitoring. But characteristics of sensor nodes, e.g., expensive wireless communication, high probability of failure or malfunction and the unstructured nature of DSN, make routing in DSN a challenging problem. Traditional routing protocols in DSN are based mostly on flooding (Directed Diffusion[1]) or random-walk (Rumor routing [1], ACQUIRE [3], etc.). Flooding causes huge communication overhead due to frequent route discovery, especially for one-shot query and for large-scale networks. Though asymptotically, random-walk shows good performance, in practice it causes high latency and without directionality and proper TTL, sometimes fails to find resource. We note that many physical phenomena follow decay law. For example, if some location’s temperature is 100C, then nearby locations temperature should be correlated with that based on distance. So, routing protocols can use this natural gradient as an important attribute to forward the query towards source. A proactive informative driven protocol is proposed in [4] for querying and routing in sensor net. It uses proactive information utility measurement to select optimal node and guide query routing, which creates extra overhead at low query rate due to exchange of information between neighbors and leader. Also that protocol does not handle scenarios with local maxima or minima or multiple sources. To overcome these limitations, in this paper we propose a novel energy efficient, fully distributed and reactive routing protocol based on gradient of event’s effect for environmental monitoring sensor networks. Our protocol handles local and isolated maxima or hole of information using simulated annealing concepts.