Poland has poor water resources. Moreover, they are unevenly distributed in space and time. Some types of human activity diminished water resources and increased the frequency of extreme phenomena such as floods and draughts. The development of rural areas depends on the quality and quantity of water resources. Suitable water management in rural areas can help enlarge water resources and minimize the negative effect of agriculture on natural flora and fauna. It should also allow for the increase of biological diversity. One of the methods to improve water conditions is by increasing the retention abilities (water harvesting) of small basins. Field studies and approximate calculations showed that treatments consisting in the increase of swampy areas, number of water pools and small water reservoirs, elevating water level in eroded rivers and canals, improvement of the soil structure, regulation of outflows from the drainage systems, etc. can significantly enlarge water resources in river basins. Proper water management should enable the supply of good quality water both for the natural environment and for the agricultural and municipal needs.