Phosphorus discharges are projected to increase more rapidly than those of nitrogen and silicon (Figure 5.9, Panel B), leading to deterioration in the natural balance of coastal marine ecosystems. Another driver exacerbating this trend is the rapid growth in the number of dams worldwide. Dams cause sediment with silicon to settle down in the reservoir and lower the sediment loading in rivers downstream, thereby reducing the level of silicon. This imbalance increases the risk of harmful algal blooms. As these are not included in the model calculations, the projected nutrient discharges to rivers and the sea may be underestimated. This section measures the number of people without access to improved water sources and to basic sanitation, as reported by the Joint Monitoring Programme.