Joaquín de Montserrat was named viceroy of New Spain early in 1760. The transfer of power was made September 19, 1760 in Otumba, and his formal entry into Mexico City was October 6, 1760. Among his immediate and most important concerns was the organization of a true colonial army. As he passed through Puebla he reviewed a battalion of militia formed of Negroes and Mulattoes. Their arms were very irregular, and the new viceroy made a formal request to Spain for new rifles to arm them. In 1761 there was an epidemic of smallpox that principally attacked the Indians. Estimates were 14,600 dead in Mexico City and up to 80,000 in Puebla. The government nearly emptied its coffers  to provide what palliative assistance was possible. Viceroy Montserrat took economy measures, ordered the collection of back taxes, and prohibited hoarding of foodstuffs and merchandise. On November 20, 1761, Mayas under Jacinto Canek rose in rebellion in Cisteil, Yucatan. Canek was captured, and on December 14, 1761 he was tortured and quartered in the plaza of Valladolid. Other disasters during Montserrat's term of office included a major flood in Guanajuato that paralyzed the operation of the silver mines , and another epidemic  that caused many deaths . He also had to send military assistance to Sonora, where a revolt of Pimas and Seris had broken out against their maltreatment by the Spanish colonists. The rebels had killed the garrisons of two presidios and the governor before escaping to the mountains, where they were finally subdued.
Question: What disaster happened in Guanajuato?
Answer: a major flood