They allow people to move easily between the countries. Also more share a common currency.
Answer:
In the upper reaches (also known as the source) the gradient is at its steepest because of vertical erosion. This changes further downstream as lateral erosion (side to side) from the river and deposition start to replace vertical erosion as the dominant process. Finally, the river really flattens out as it approaches the mouth as deposition become dominant.
Quality inputs (improved seeds and fertilizers) are essential to raising productivity (yields per unit area planted) under both the rainfed and irrigated conditions. In addition, strong extension and advisory services are important for enhancing the adoption and efficiency of improved inputs.
a ciência de examinar e mapear corpos de água, como mares, lagos e rios.
the study of the physical features of the earth and its atmosphere, and of human activity as it affects and is affected by these, including the distribution of populations and resources, land use, and industries.