Eresma River

River Eresma
The Eresma River as it passes through Los Redondillos (Los Huertos,Segovia)
Location
Country	Spain
Region	Castile and León
Physical characteristics
Mouth	Adaja River
• coordinates	41°26′38″N4°45′15″W
Length	134 km
Basin features
Progression	Adaja→Douro→Atlantic Ocean

TheEresmais a river in central Spain. It flows throughCastile and León(specifically the provinces ofSegoviaandValladolid). It has a total length of 134 km and drains a basin with an area of 2,940 km².

Name

The name of the river has been derived from theIberian"Iri-sama" which means "that which surrounds the big city". The city referred to here is notSegoviaitself as sometimes thought, but rather the town ofCocalocated some 50 km away.

Geography

The Eresma River starts in Valsaín valley of theSierra de Guadarrama,where the confluence of several streams forms the river. Most of these streams descend from the slopes of mountains like Peñalara,Siete Picos,andMontón de Trigo.Its most important tributaries are Moros and the Voltoya that flow northward. After passing throughSan IldefonsoandPalazuelos,it reaches the city ofSegovia,which it surrounds in a closedmeander.Eresma river then runs northwest, passing nearHontanares,Los Huertos,Bernardos,Navas de Oro,Coca, andVilleguillo.It enters the province of Valladolid throughOlmedo,Pedrajas,Alcazarén,and Hornillos. Later it flows from the right into theAdajainMatapozuelos.

The Eresma River has apluvio-nival regime,which means that it has a period of high water flow in the autumn and winter season in proportion to precipitation and a short, violent water flow in the spring when the snow melts.