Matching each modification to its effect on an ecosystem:
a) Many desert regions in the West were transformed into lush urban areas and farmlands. This modification drastically altered local ecosystems, introducing new species and agricultural practices, and changing the natural landscape and water usage patterns.
b) Water bodies in the Owens Valley and its surrounding areas began to dry up. This is a direct consequence of d) the construction of the Los Angeles Aqueduct, which diverted water away from these areas to supply Los Angeles, leading to significant ecological changes due to reduced water availability.
c) Runoff containing disease-carrying organisms contaminated soil and caused water pollution. This is often a consequence of e) the construction of large highways, which can lead to increased runoff from roads carrying pollutants and pathogens into nearby soil and water bodies.
f) Damming of the Colorado River led to significant ecological changes, including altered water flow, changes in sediment transport, and impacts on aquatic and riparian habitats. This intervention has had profound effects on the ecosystem, including changes in fish populations and riverine environments.