A device for irrigating soil has a chassis having wheels or tracks for motion, the chassis having one or more water sprinklers with streams directed at the soil, a water storage tank, and a sloped catchment surface having one or more sloped planes or curved surfaces for receiving water from a refill station into the water storage tank, wherein, under the control of an electronic circuit, the irrigation device can refill the water tank by positioning any part of the catchment surface under a water stream from the refill station. A method has the steps of measuring soil moisture at remote locations, refilling the mobile robot using a gravity feed water stream, defining a route for distribution of water, traversing the irrigation routes, refilling water according to soil moisture measurements, storing photovoltaic energy in a battery, and rotating, to a compass heading such that the photovoltaic array is optimally oriented.
