I’m near the Warrumbungle range, lightly wooded, and our garden irrigation dam is about 400m away. It has a solar panel, a battery, a control unit, and a tiny pump. On remote command from the house network, it pumps every few weeks up to a storage tank above the level of the garden. The tank has a flow sensor and another control unit. The house has a control unit with WiFi to house network. Here’s a system diagram.
We used three Arduino Pro Mini modules from Little Bird Electronics, three Radiometrix BiM1 VHF narrow band FM transceiver modules at 151 MHz, and the Virtual Wire library for Arduino.
The range of the system ended up being about 6km, with omnidirectional antennas, because of the frequency chosen. I was going to switch to directional antennas if necessary. I’d probably use different modules today, and the Virtual Wire library has been abandoned though it still works and there is a different library that can be used.