Food and agriculture are the largest consumers of water, requiring one hundred times more than we use for personal needs. The amount of water involved in agriculture is significant and most of it is provided directly by rainfall. Irrigation allows the land that does not receive enough precipitation annually to become land that can be used for productive agriculture. Agricultural practices may also have negative impacts on water quality. Improper agricultural methods may elevate concentrations of nutrients, fecal coli forms, and sediment loads. Groundwater contamination occurs when the pesticides, livestock waste and fertilizers infiltrate through the soil and eventually reach the groundwater, which is called leaching. Crops also rely on this water source and have very specific water requirements, and these vary depending on local climate conditions. High salt concentrations limit the amount of water a plant can take up; resulting in high plant stress and decreased crop yields. Grazing and other agriculture practices may intensify erosion processes raising sediment input to nearby water sources.